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Asthma incidence in wood-processing industries in Finland in a register-based population study


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This register-based population study determined incidence rates of clinically verified asthma among woodworkers, other blue-collar workers, and administrative personnel employed in wood-processing industries in Finland. Exposure to wood dust was under special scrutiny. All Finns employed in wood-processing industries were followed for asthma incidence via record linkage in the years 1986-1998. Incident cases included people with asthma reimbursed for medication by the national health insurance or registered as having occupational asthma. Age-adjusted incidence rates and relative risks (RR) by gender were estimated for wood workers, other blue-collar workers, and administrative employees (referents) in wood industries. The relative risk of asthma was increased for all woodworkers among both genders [men: RR 1.5, 95% confidence interval (95% CI) 1.2-1.8; women: RR 1.5, 95% Cl 1.2-1.7]; a similarly elevated risk was also found for other blue-collar workers (men: RR 1.5, 95% Cl 1.2-1.8; women: RR 1.4, 95% Cl 1.2-1.6) in the same wood industries. Statistically increased relative risks were found for low and medium exposure to wood dust, but not for high exposure. Altogether 217 of the 4074 clinically verified asthma cases were reported as occupational asthma in the Finnish Register on Occupational Diseases. The incidence rates for asthma were significantly increased both among the woodworkers and the other blue-collar workers in wood industries but without a clear dose-response. Cases recognized as occupational asthma accounted for only a small part of the total asthma excess, indicating that much of the work-related asthma excess remains unrecognized in these industries.
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66 Scand J Work Environ Health 2008, vol 34, no 1
Original article
Scand J Work Environ Health 2008;34(1):66–72
Asthma incidence in wood-processing industries in Finland in a register-
based population study
by Pirjo Heikkilä, PhD,
Rami Martikainen, MSc,
Kari Kurppa, MD,
Kirsti Husgafvel-Pursiainen, PhD,
Antti Karjalainen, MD
Heikkilä P, Martikainen R, Kurppa K, Husgafvel-Pursiainen K, Karjalainen A. Asthma incidence in wood-processing
industries in Finland in a register-based population study. Scand J Work Environ Health. 2008;34(1):66–72.
This register-based population study determined incidence rates of clinically verified asthma among
woodworkers, other blue-collar workers, and administrative personnel employed in wood-processing industries
in Finland. Exposure to wood dust was under special scrutiny.
All Finns employed in wood-processing industries were followed for asthma incidence via record
linkage in the years 1986–1998. Incident cases included people with asthma reimbursed for medication by the
national health insurance or registered as having occupational asthma. Age-adjusted incidence rates and relative
risks (RR) by gender were estimated for wood workers, other blue-collar workers, and administrative employees
(referents) in wood industries.
Results The relative risk of asthma was increased for all woodworkers among both genders [men: RR 1.5, 95%
confidence interval (95% CI) 1.2–1.8; women: RR 1.5, 95% Cl 1.2–1.7]; a similarly elevated risk was also found
for other blue-collar workers (men: RR 1.5, 95% Cl 1.2–1.8; women: RR 1.4, 95% Cl 1.2–1.6) in the same wood
industries. Statistically increased relative risks were found for low and medium exposure to wood dust, but not
for high exposure. Altogether 217 of the 4074 clinically verified asthma cases were reported as occupational
asthma in the Finnish Register on Occupational Diseases.
Conclusions The incidence rates for asthma were significantly increased both among the woodworkers and the
other blue-collar workers in wood industries but without a clear dose–response. Cases recognized as occupational
asthma accounted for only a small part of the total asthma excess, indicating that much of the work-related asthma
excess remains unrecognized in these industries.
Key terms attributable fraction; exposure; occupational disease; relative risk; wood dust.
Finnish Institute of Occupational Health, Helsinki, Finland.
Correspondence to: Dr P Heikkilä, Finnish Institute of Occupational Health, Topeliuksenkatu 41 aA, FI-00250 Helsinki,
Finland. [E-mail:]
Asthma is a common disorder; 5–10% of the general
population in many countries is affected by the disease.
A recent Finnish study indicated that the attributable
fraction of work in adult-onset asthma is 29% for men
and 17% for women (1). Other studies suggest that the
proportion of new or exacerbated asthma cases due to
workplace exposures ranges between 9% and 26% (2–6).
Although over 250 agents have been documented as
being responsible for sensitizer-induced occupational
asthma, our knowledge about the multiplicity of caus-
ative factors and the pathogenic mechanisms involved
in the development of occupational asthma still remains
incomplete (7).
As concerns work in wood processing, asthma has
been attributed to dust from many different tree species,
on the basis of case reports and epidemiologic studies (8,
9). The proportion of all cases of occupational asthma
due to wood dust has been reported to be some 6–11%
(8). Asthma induced by western red cedar has been
frequently documented for sawmill workers, with an
apparent dose–response relationship (10–14). The stud-
ies proposing a relationship between exposure to other
softwood species and asthma have used self-reported
asthma (11) and clinically diagnosed asthma (15, 16)
as outcomes.
Finland provides an opportunity to study the varia-
tion in asthma incidence in a country in which the cost
of asthma medication for clinically verified asthma is
reimbursed and registered by a national health insurance
scheme that covers the entire population. A personal
identification code allows linkage of the register infor-
mation with data on employment and occupation avail-
able from the Finnish Population Census. The results
from such data linkage have identified a large number
Scand J Work Environ Health 2008, vol 34, no 1 67
Heikkilä et al
of occupations with significant excesses of asthma in-
cidence rates (1).
Specific bronchial challenge testing of individual
workers has shown that wood dusts common in Finn-
ish industries (spruce, pine, birch) cause asthma. A few
cases a year are registered in the Finnish Register on
Occupational Diseases. Yet it is not known how high
the risk actually is and which industrial sectors may be
particularly at risk. Therefore, our present analysis com-
pared the incidence rate of asthma in a variety of Finnish
wood-processing industries. We used the data from the
national reimbursement register for asthma medication,
the Finnish Register on Occupational Diseases, and
the Finnish Population Census for the occupation and
industrial sector of employment from three census co-
horts (1985, 1990, and 1995) to estimate the incidence
rates of asthma for woodworkers in wood-processing
Study population and methods
Study population and design
All Finns who were 20–59 years old, without preexist-
ing asthma on 31 December 1985, 1990, and 1995, and
who were employed according to the population census
in 1985, 1990, or 1995 in certain industrial sectors were
followed for asthma incidence rates during the years
1986–1990, 1991–1995, and 1996–1998, respectively.
The industrial sectors included in the asthma follow-
up were as follows (the codes are those used by the
Statistical Classification of Economic Activities in the
European Community, NACE Rev 1, 1990): (i) forestry,
logging and related services (02.0), (ii) sawmilling and
planing of wood and impregnation of wood (20.1), (iii)
manufacture of veneer sheets and manufacture of ply-
wood, laminboard, particle board, fiber board and other
panels and boards (20.2), (iv) manufacture of builders
carpentry and joinery (20.3), (v) manufacture of wooden
containers (20.4), (vi) manufacture of other products
of wood and manufacture of articles of cork, straw and
plaiting materials (20.5), (vii) building and repairing of
ships and boats (35.1), (viii) manufacture of furniture
(36.1), (ix) building of complete constructions or parts
thereof and civil engineering (45.2), and (x) building
completion (45.4).
On the average, about 158 000 blue-collar workers
(141 187 men and 16 937 women) and about 13 000
workers (4628 men and 8211 women) in
the three census cohorts were employed in these wood-
processing industries.
The follow-up was performed using the unique
personal identification code in accessing two national
registers, the Drug Reimbursement
Register of the Social
Insurance Institution of Finland and the Finnish Register
on Occupational Diseases, housed in the Finnish Insti-
tute of Occupational Health. Duplicate notifications in
two registers were identified using the indivitual per-
sonal identification codes. For each follow-up period,
the cases and person-years were calculated according
to occupation and the sector of economic activity in
which the person was working at the start of the fol-
low-up. People could contribute to the person-years of
follow-up periods, provided they had not been
defined as an
incident case of asthma before the start
of the follow-up period
and were still employed in the
selected industrial sectors at the start of the follow-up
period. Therefore, the number
of persons under follow-
up is given as an average of the
three follow-up periods
and not as an absolute number of the
different persons
followed. The occupation was known for 99% of those
employed in each of the three censuses. The study
protocol was approved by the ethics committees of the
participating institutions.
Classification of occupation of the persons and eco-
nomic activity of their employers
Information on the professional status, current occupa-
tion, and
economic activity of employees is recorded for
every employed
person in the Finnish Population Cen-
sus. The occupational codes are based on a version of
the International Standard
Classification of Occupations,
1988 (ISCO-88 COM). The economic activity codes
partly follow an extended classification of the Standards
Industrial Classification of all Economic Activities by
the United Nations in 1968 and partly the Statistical
Classification of Economic Activities in the European
Community, 1990 (NACE Rev 1). All of the economic
activity codes were converted to NACE Rev 1.
Information on occupation was cross-sectional from
the time
of the census. Those aged <20 years were not
because a change of occupation and migration
between education
and worklife make the employment
status and occupation at
the start of the follow-up less
reliable indicators of the occupational
status during the
5-year follow-up. Similarly those aged >59 years were
not followed
because most of those employed at the start
of the follow-up
would no longer have been employed at
the end of the follow-up; the time period when they left
the labor market was not known.
Occupational exposure to wood dust
The occupations in the selected 10 wood industries were
grouped into the following three categories: woodwork-
ers (with direct exposure to wood dust), other blue-col-
lar workers (with possible exposure to wood dust), and
unexposed persons (administrative workers; reference
68 Scand J Work Environ Health 2008, vol 34, no 1
Asthma incidence in wook-processing industries
group). The jobs coded as woodworkers were forestry
workers and lumberjacks, timber men, sawyers, plywood
and fiberboard workers, construction carpenters, wooden
boat builders, coach-body builders, bench carpenters,
cabinetmakers and joiners, woodworking machine op-
erators, wooden surface nishers, woodworking oc-
cupations not elsewhere classified, and cleaners. The
group of other blue-collar workers in wood-processing
industries consisted of workers with such occupations
as technicians, painters, welders, assemblers, machine
mechanics, forklift and other drivers, and packers. Some
persons in this group have also been exposed to wood
dust, including mechanics and assemblers when repair-
ing wood-processing machines. Those employed in
administrative, managerial, and clerical
work in the
selected industries were considered to be unexposed and
were used as a reference group. The incidence rates for
asthma in these three occupational groups in the selected
10 industrial sectors were followed.
Incidence rates were also calculated according to the
estimated level of wood dust exposure. Occupational
exposure to wood dust was assessed in 120 job-indus-
try combinations as an annual mean of the total dust
concentration. [Total dust concentrations correspond
to approximately 50% of the inhalable dust concentra-
tion.] The workers in the 10 selected industrial sectors
were classified into the following five categories: high,
medium or low exposure to wood dust, unknown expo-
sure, and reference group (table 1). The classification of
exposure levels was based on measurements carried out
by the Finnish Institute of Occupational Health in the
selected industrial sectors (17).
Definition and ascertainment of cases
Incident cases were collected from the Medication
Reimbursement Register of the Social Insurance Institu-
tion. In Finland, asthma is classified as a chronic disease
for which the cost of medication can be reimbursed at
a higher than ordinary level. To receive the compensa-
tion, the patient has to apply for the entitlement from
the Social Insurance Institution, submitting a medical
certificate signed by a pulmonary specialist, along with
the application. For compensation to be granted, the
disease has to fulfill the diagnostic and severity criteria
of asthma (1), including objective data of reversible
bronchial obstruction and a persistent pattern of disease.
The health insurance, which includes the drug-reim-
bursement system, covers the entire Finnish population,
and consequently all Finnish patients with asthma fulfill-
ing the criteria are identifiable in the register. The only
exceptions are patients with recognized occupational
asthma, who receive full compensation for medication
from the Statutory Accident Insurance. The recogni-
tion of occupational asthma necessitates a diagnosis of
asthma made by a pulmonary specialist and his or her
evidence of a specific causal association between the
persons occupational exposure and the disease.
In our current study, a person was defined as having
clinically verified asthma if he or she received rights for
reimbursement for asthma medication from the Social
Insurance Institution or was registered as having occu-
pational asthma in the Finnish Register on Occupational
Diseases. In this study, the concept persistent asthma
is dened as asthma needing regular medication and
fulfilling the criteria for asthma medication reimburse-
ment rights. The date of the application (Social Insur-
ance Institution) or the date of the registration report
(Finnish Register on Occupational Diseases) was used
as a proxy for the date of diagnosis. As our follow-up
was based on the attribution of special reimbursement
rights for asthma medication, a person became classi-
fied as a case of asthma only when the criteria of these
rights were fulfilled, even if he or she may have had
asthma-like symptoms before. It could also be that those
who had had childhood asthma and who had recovered
before 1970 when asthma became eligible for special
reimbursement rights and who again were afflicted with
asthma during the follow-up after 1985 were classified
as incident cases of adult-onset asthma.
Statistical analyses
The men and women were analyzed separately since
the overall incidence of adult onset asthma is higher
for women than for men, and this difference applies to
Finland as well (18, 19). In addition, men and women
may perform different tasks in a given occupation, and
so their exposure patterns may differ. The incidence
rate for the exposure variables, wood dust exposure
category, and industrial sector was calculated by sum-
ming up the cases and person-years from the three
census cohorts and dividing the total number of cases
the accumulated person-years under follow-up in each
respective group.
Incidence rate ratios [relative risks
(RR)] and their 95% confidence
intervals (95% CI) for
the wood-dust exposure categories and woodworkers in
Table 1. Wood-dust exposure categories for woodworkers and the
number of job–industry combinations in each category.
Category Total dust concentration Number of job–industry
) combinations
Low 0.02-<0.5 68
Medium 0.5-<1.5 40
1.5 12
Jobs classified as high exposure (the codes refer to economic activity
codes; see the Classification of Occupation of the Persons and Economic
Activity of their Employers section for details): timber men (45.4), saw-
yers (36.1 & 45.4), woodworking machine operators (20.3 & 36.1),
bench carpenters, cabinetmakers, joiners, etc (36.1 & 45.4), cleaners
(20.1, 20.2 & 36.1).
Scand J Work Environ Health 2008, vol 34, no 1 69
Heikkilä et al
the selected industries were estimated by a log–linear
model (Poisson distributed), using person-years as an
offset variable. Age at the start of the follow-up (20–29,
3039, 4049, and 50–59 years) was included in the
model. Those employed in administrative, managerial,
and clerical
work in the selected industries were used as
a reference group in both models. SAS software (SAS
Inc, Gary, NC, USA) was used in the analyses.
The attributable fraction (AF) of the asthma cases
caused by occupational exposure in wood-processing
industries (ie, the work-related fraction of asthma among
woodworkers and other blue-collar workers) was esti-
mated according to the equation AF = (RR-1)/RR (20);
the 95% confidence intervals of the attributable fractions
were calculated from the 95% confidence intervals of
the corresponding relative risks. The number of work-
related asthma cases among the woodworkers and other
blue-collar workers was determined as N × AF, where N
was the number of all asthma cases in a group.
The incident rates and relative risks for clinically veri-
fied asthma among woodworkers and other blue-collar
workers in the wood-processing industries in Finland are
presented in table 2. Out of all the blue-collar workers
(141 197 men, 16 937 women) in 10 selected wood-pro-
cessing industries, 34% men and 26% women, respec-
tively, were classified as being exposed to wood dust.
The relative risk for asthma was significantly increased
for all of the woodworkers among both genders, and an
elevated risk was also found for other blue-collar work-
ers employed in the same wood industries. Classification
by the intensity of wood dust exposure indicated that, of
the male workers, 4% were persons with high exposure,
8% had medium exposure, and 23% had low exposure.
The corresponding values for the women were 5%, 11%,
and 10%. No clear dose–response to wood dust exposure
was indicated. Nevertheless, significantly increased rela-
tive risks for asthma were found for the groups with low
or medium exposure, but not for the group with high
exposure (table 2).
From the various sectors of the wood-processing
industries, the risk was significantly increased for male
woodworkers in 7 of the10 industrial sectors studied
(table 3). The asthma risks were highest in the manu-
facture of wooden containers (RR 2.5, 95% Cl 1.3–4.6),
and in sawmilling and wood planing (RR 1.9, 95% Cl
1.52.5). For the female woodworkers, the risk was
significantly increased in 4 of the 10 industrial sectors,
the highest risk being determined for sawmilling and the
impregnation of wood (RR 1.8, 95% Cl 1.3–2.4). The
asthma incidence per 1000 person-years did not differ
significantly between the woodworkers (1.7 for the men
and 3.2 for the women) and other blue-collar workers
working in wood-processing industries (1.8 for the men,
2.9 for the women) (table 2).
The calculated fraction of asthma cases attributable to
work-related factors was 31% (95% CI 15–45) for both
the male and female woodworkers and 30% (95% CI
12–43) and 26% (95% CI 13–38) for the other male and
female blue-collar workers, respectively (table 2).
On the basis of the attributable fractions estimated in
table 2, a total of 1213 of all 4074 asthma cases identi-
fied in the 10 selected wood industry sectors would be
in excess (ie, attributable to work-related factors). How-
ever, only 217 were registered in the Finnish Register
on Occupational Diseases as occupational asthma, varia-
tion occurring between industries. In addition to wood
dust, other exposures, such as to formaldehyde, epoxy
Table 2. Incidence rates (per 1000 workers × year
), relative risks (age-adjusted), and work-related attributable fractions (AF) for asthma
among male and female workers. The woodworkers have been subdivided according to the exposure-level categories. (RR = relative risk,
95% CI = 95% confidence interval)
Categories Men Women
Cases Popula
Incidence RR 95% Cl AF Cases Popula- Incidence RR 95% Cl AF
rate (%) tion
rate (%)
86 4 628 1.4 1.0 ·· ·· 223 8 211 2.0 1.0 ·· ··
1189 50 218 1.7 1.5 1.2–1.8 31 286 6 503 3.2 1.5 1.2–1.7 31
Low exposure 785 33 226 1.7 1.4 1.1–1.7 · 110 2 536 3.1 1.4 1.2–1.8 ·
Medium exposure 317 11 905 2.0 1.7 1.4–2.2 · 134 2 742 3.7 1.6 1.3–2.0 ·
High exposure 87 5 087 1.3 1.2 0.9–1.6 · 42 1 225 2.6 1.2 0.8–1.6 ·
Other blue-collar workers
2181 90 979 1.8 1.4 1.1–1.8 30 418 10 434 2.9 1.4 1.2–1.6 26
All blue-collar workers 3370 141 197 1.8 1.4 1.1–1.8 30 704 16 937 3.0 1.4 1.2–1.6 29
Arithmetic mean of the population under follow-up in 1986–1990, 1991–1995, and 1996–1998,
Administrative, managerial, and clerical workers in the selected wood industries.
Woodworkers in the selected wood industries included the occupations in which direct exposure to wood dust was estimated to occur.
Other blue-collar workers included the occupations in which exposure to wood dust was unknown.
70 Scand J Work Environ Health 2008, vol 34, no 1
Asthma incidence in wook-processing industries
compounds, isocyanates, microorganisms, or glues, have
been registered in the Finnish Register on Occupational
Diseases as causative agents for occupational asthma in
wood-processing sectors (table 4).
We found significantly elevated risks of asthma both
for wood workers and other blue-collar workers em-
ployed in wood-processing industries. In our study,
the case ascertainment was accomplished through two
national registers that rely on diagnoses made by pul-
monary specialists based on strict clinical criteria for
a persistent form of asthma (asthma needing regular
medication). This definition is rather specific but, at the
same time, more restrictive than those typically used
in epidemiologic studies. Consequently, using such a
definition as physician-diagnosed persistent asthma
will result in high specificity and low sensitivity, and it
may in fact underestimate the frequency of asthma. The
excess observed in association with work may repre-
sent two types of disease, new-onset persistent asthma
without a history of asthma or preexisting mild disease
that the work-related exposure may have aggravated
so that it deteriorated sufficiently to fulfill the criteria
Table 3. Incidence rates (per 1000 workers × year
), relative risks (age-adjusted) for asthma in wood industries. (RR = relative risk, 95%
CI = 95% confidence interval)
Categories Men Women
Cases Popula- Incidence RR 95% Cl Cases Popula- Incidence RR 95% Cl
rate tion
86 4 628 1.4 1.0 ·· 223 8211 2.1 1.0 ··
c, d
1189 50 218 1.7 1.5 1.2–1.8 286 6503 3.2 1.5 1.2–1.7
Forestry and logging (02.0) 320 13 145 1.8 1.5 1.2–1.8 8
256 · · ·
Sawmilling (20.1) 173 5 647 2.3 1.9 1.5–2.5 55 995 4.0 1.8 1.3–2.4
Manufacture of wooden boards (20.2) 55 2 006 2.1 1.7 1.2–2.5 76 1541 3.7 1.6 1.3–2.1
Manufacture of builders’ carpentry (20.3) 103 4 375 1.7 1.6 1.2–2.2 45 922 3.7 1.7 1.2–2.5
Manufacture of wooden containers (20.4) 11 327 2.7 2.5 1.3–4.6 1
60 · · ·
Manufacture of other wood products (20.5) 15 652 1.7 1.5 0.9–2.6 3
123 · · ·
Building and repairing ships and boats (35.1) 15 1 113 1.0 0.9 0.5–1.5 7
290 · · ·
Manufacture of furniture (36.1) 65 4 084 1.2 1.1 0.8–1.5 26 952 2.0 0.9 0.62–1.40
Building of complete constructions (45.2) 412 17 973 1.7 1.3 1.1–1.7 62 1301 3.4 1.5 1.1–2.0
Building completion (45.4) 20 895 1.8 1.7 1.1–1.8 3
63 · · ·
Arithmetic mean of the population under follow-up in 1986–1990, 1991–1995, and 1996–1998.
Administrative, managerial, and clerical workers in the selected wood industries.
If the number of cases was <10, the incidence rates and relative risks have not been reported.
Code of the economic activity (see the Classification of Occupation of the Persons and the Economic Actvitiy of their Employers) in parentheses.
Table 4. Estimated work-related asthma cases and reported occupational asthma cases among the workers in the 10 wood industry sec-
tors in the Finnish Register on Occupational Diseases in 1986–1998.
Industrial sectors
Finnish Register on Occupational Diseases
Cases Coded causative agent
Forestry, logging and related services (02.0) 328 99 1 Animal epithelium
Sawmilling and planing of wood and impregnation of wood (20.1) 228 107 18 Spruce; wood not specified
Manufacture of wooden and fiber boards (20.2) 131 52 39 Isocyanates; formaldehyde; molds; pine; spruce; birch;
Manufacture of builders carpentry and joinery (20.3) 148 58 28 Isocyanates; formaldehyde; pine; obeche; wood not
Manufacture of wooden containers (20.4) 12 6
Manufacture of other products of wood (20.5) 18 4 9 Formaldehyde; pine; obeche; wood not specified
Building and repairing of ships and boats (35.1) 22 1 Teak
Manufacture of furniture (36.1) 91 4 13 Formaldehyde; spruce; beech
Building of complete constructions (45.2) 474 123 10 Isocyanates; paints; pine; obeche
Building completion (45.4) 23 10 1 Epoxy paints; obeche
Woodworkers 1 475 468 119 ·
Other blue-collar workers 2 599 745 98 ·
Code of the economic activity (see the Classification of Occupation of the Persons and the Economic Actvitiy of their Employers) in parentheses.
The estimated cases have been calculated on the basis of the work-related attributable fractions and the numbers of cases in table 3.
Cases Estimated
(N) work-
Scand J Work Environ Health 2008, vol 34, no 1 71
Heikkilä et al
for reimbursement established by the Social Insurance
Institution of Finland.
In the wood-processing industries, the asthma in-
cidence rates were equally elevated among the wood
workers and other blue-collar workers when they were
compared with an unexposed (white-collar) reference
group from the same industries. The wood workers in
this study were grouped according to the intensity of
wood dust exposure. However, part of other blue-col-
lar workers has also been exposed to wood dust, and
other respiratory irritants and allergy-causing airborne
contaminants are present in these industries. Both the
woodworkers and other blue-collar workers may have
been exposed to such other exposures. This possibility
could mean either that even a rather low exposure to
wood dust can increase the risk of developing persistent
asthma or it could be that, in the group of other blue-
collar workers, also other (nonwood dusts) industrial
exposures play an important role. There is increasing
evidence that asthma and other respiratory symptoms
occur already at low wood dust levels (11, 16, 21). The
relation between occupational exposures and asthma is
complicated. Generally, a single causal agent is identi-
fied as a causative agent in occupational asthma, whereas
wood dusts and emissions from fresh wood are complex
mixtures of chemicals, particles, and biohazards that
make it more difficult to ascribe causality.
Although the relative risk for wood workers was
significantly elevated and the analysis by intensity of
wood dust exposure revealed signicantly increased
asthma risks in the low- and medium-exposure groups,
no dose–response relationship between the level of wood
dust exposure and asthma was found. However, there are
several factors that may have affected the dose–response
relationships. In addition to evidence for respiratory
health effects at low wood dust levels, early in employ-
ment, workers may choose to quit when ill or when work
conditions are perceived to cause illness such as asthma.
It has been shown that changing jobs because the current
one is causing respiratory symptoms is frequent before
the diagnosis of asthma (22). Finally, the nondifferential
misclassification of exposure may cause bias away from
the null in the medium category, whereas the overall
exposure–response trend will usually be biased towards
the null (23).
The differences between the risk estimates in differ-
ent industries were small, although the exposure patterns
of the workers differed. Wood handled in sawmills and
in wooden board industries is fresh, whereas it is dry, for
example, in the furniture industry. Over 95% of the wood
used in Finnish sawmills is either pine or spruce, the rest
being birch (24). Fresh softwood wood can emit mono-
terpenes (25) and resin acids (26). Resin acids are well-
known allergens; these causative agents are believed to
be peroxides formed from abietic acid in intense heat
(27–30). Several authors have postulated that some of
the respiratory symptoms reported for woodworkers
could be due to exposure to microbe-related agents
(eg, endotoxins) (31–33). In other, questionnaire-based
studies, sawmill workers exposed to coniferous tree spe-
cies and to other exposures have also reported current
asthma more often than referents (11, 13). In Finland,
the occupational disease register (Finnish Register on
Occupational Diseases) lists a few well-documented
cases of occupational asthma caused by exposure to
dusts from spruce or pine (table 4). Such diagnoses have
been clinically verified by bronchial challenge tests us-
ing inhalable preparations of wood dust.
An obvious question in considering the ndings
of our study is whether the comparison of the asthma
incidence of the blue-collar workers with that of the
administrative employees (managers, clerks) is valid.
If the risk of asthma were clearly related to the social
class of the employees, the finding would be distorted
by confounding. Many administrative employees belong
to a higher social class than blue-collar workers do. Our
analysis is part of a larger study of asthma incidence in
the employed workforce of Finland, which used admin-
istrative, managerial, and clerical work as reference (1,
34). To examine the possible effect of social class on
the results, we performed separate analyses using as
reference only the lower-level administrative employees
(secretaries, office clerks, bookkeepers, and similar oc-
cupations). The incidence rate of the lower-level admin-
istrative employees was similar to that of administrative
workers in general and did not change the relative risks
of the exposed occupations. We have also considered
potential confounding by smoking differences and con-
cluded that it is unlikely that such differences would
have significantly biased our risk estimates (1, 34).
In conclusion, we found an increased incidence
of asthma in wood-processing industries, not only for
wood workers directly exposed to wood dust but also
for other blue-collar workers employed in the same
wood industry sectors. In both of these groups, the
attributable fraction of the work-related factors of the
asthma incidence was about 31%. Cases recognized as
occupational asthma accounted for only a small part of
the total asthma excess. This finding indicates that much
of the work-related asthma excess remains unrecognized
in these industries.
We are indebted to Marianne Johnson from Statistics
Finland, Timo Klaukka from the Finnish Social Insur-
ance Institution, and Anja Saalo and Ilpo Mäkinen from
the Finnish Register on Occupational Diseases for their
assistance in creating the datales.
72 Scand J Work Environ Health 2008, vol 34, no 1
Asthma incidence in wook-processing industries
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Received for publication: 6 March 2007
... Asthma was defined in varying ways across studies. For example, five papers identified asthma cases using worker questionnaire responses [28,31,33,36,37], and one study used insurance data and ICD-10 codes to identify population-based asthma incidence [38]. A further study included a nested case-control analysis and performed objective measures of asthma including PEFR variability, BHR and BDIR [39]. ...
... Studies using serial PEF recordings to support a diagnosis of asthma included Norrish et al., who identified 12% of exposed furniture workers with that condition [28]. Lipscomb et al. reported similar prevalence, with 10.6% of their exposed population reporting 'ever asthma', and 8% reporting an asthma attack in the last 12 months [37] In a large Finnish epidemiological study, Heikkilä et al. identified a relative risk (RR) of asthma of 1.5 for both male and female woodworkers compared with the general Finnish population, similar to that reported in other non-exposed blue-collar workers (RR 1.4) [38]. Pérez-Ríos et al. found comparable results in their metaanalysis of 19 studies, with RR of 1.5 for asthma in woodworkers [40]. ...
... The only meta-analysis included in the review reported an increased RR for asthma in woodworkers of 1.5 compared with the general population [40]. Heikkilä et al. found similar RRs (1.5 in both female and male woodworkers) comparable to blue-collar workers in the same industry, although did not identify a dose effect [38]. Inclusion in the study depended on inclusion in a national registry, potentially missing workers with a past, or missed, asthma diagnosis. ...
Background: Wood dust is a common cause of occupational asthma. There is potential for high exposure to wood dust during furniture and wood manufacturing processes. Aims: To evaluate the evidence for non-neoplastic respiratory ill health associated with work in the furniture and wood manufacturing sector. Methods: A systematic review was performed according to PRISMA guidelines. Articles were graded using SIGN (Scottish Intercollegiate Guideline Network) and MERGE (Methods for Evaluating Research Guidelines and Evidence) criteria, with data grouped by study outcome. Results: Initial searches identified 1328 references, from which 55 articles were included in the review. Fourteen studies were graded A using MERGE or >2++ using SIGN. All but one paper describing airway symptoms reported an increased risk in higher wood dust exposed workers in comparison to lower or non-exposed groups. Five studies reporting asthma examined dose response; three found a positive effect. The relative risk for asthma in exposed workers in the single meta-analysis was 1.5 (95% CI 1.25-1.87). Two studies reported more obstructive lung function (forced expiratory volume in 1 s [FEV1]/forced vital capacity < 0.7) in exposed populations. Excess longitudinal FEV1 decline was reported in female smokers with high wood dust exposures in one study population. Where measured, work-related respiratory symptoms did not clearly relate to specific wood immunoglobulin E positivity. Conclusions: Work in this sector was associated with a significantly increased risk of respiratory symptoms and asthma. The evidence for wood dust exposure causing impaired lung function is less clearly established. Further study is required to better understand the prevalence, and causes, of respiratory problems within this sector.
... Although an increased risk was detected for "cabinet and wood furniture makers," decreased risks were observed for other woodworkers, including "carpenters and related" and "sawmills, planing mills, and shingle mills." Although there is a wellrecognized increased risk of asthma among woodworkers, associations may be specific to certain wood species and could also be influenced by additional factors such as the wood particle sizes generated during different tasks (12,14,34,35). Studies of western cedar, which only grows in western Canada, have reported particularly elevated risks of NOAA among workers, likely attributable to plicatic acid (4,11,34). ...
Given that approximately 15% of new onset adult asthma cases originate due to exposures in the workplace, there is a need for systematic and ongoing monitoring of risk among workers. OBJECTIVES: To characterize the risk of new onset adult asthma among workers in Ontario. METHODS: We utilized 575,379 provincial accepted time-loss workers' compensation claimants data linked to physician billing data. Workers at-risk of new onset adult asthma were followed from cohort entry date to date of diagnosis, emigration, age 65, death, or end of study period. The case definition required 2+ records for asthma within a 12-month period, within a 3-year time window following cohort entry. Cox regression models were used to generate birth year and sex-adjusted hazard ratios (HR) by occupation, industry and exposures identified using a job exposure matrix (JEM). Sex-stratified risk estimates were also generated. RESULTS: Increased risks were detected among well-recognized groups including bakers (HR 1.60, 95% confidence interval (CI)=1.22-2.09) and painters and decorators (HR 1.67, 95% CI=1.23-2.28). In the JEM analysis, flour and isocyanates were associated with increased risk of asthma. Concrete finishers (HR 1.93, 95% CI=1.12-3.32) and shipping and receiving clerks (HR 1.21, 95% CI=1.03-1.43) also showed elevated risk, while results varied across woodworker groups. Decreased risks were detected for nursing and farming groups. CONCLUSIONS: This practical data linkage approach was successful for examining associations across hundreds of jobs. Unexpected and previously unrecognized findings deserve further investigation and emphasize the importance of an ongoing system to guide research, as well as prevention.
... Several studies have shown that mould particles with diameters below 2.4 lm (majority of A. fumigatus particles present in indoor environments), if inhaled, present the greatest danger to human health (Górny 2004). In wood-processing environments, moulds are considered as a major harmful factor related to various symptoms (Mandryk et al. 1999;Rusca et al. 2008;Karvala et al. 2008;Jacobsen et al. 2009;Ljubičić Ć alušić et al. 2012) and respiratory diseases such as extrinsic allergic alveolitis and occupational asthma (Halpin et al. 1994a;Veillette et al. 2006;Heikkilä et al. 2008). The inhalation of large amounts of moulds (Aspergillus sp., Penicillium sp., Cladosporium sp., Rhizopus sp. and Alternaria sp) has especially been associated with the appearance of the above-mentioned respiratory disorders among wood workers (Karvala et al. 2008). ...
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Asp f 1 (ribotoxin) is the main allergen of Aspergillus fumigatus and a critical factor in provoking allergic responses and bronchopulmonary aspergillosis. This study investigated the prevalence of allergen Asp f 1 in dust samples collected at two Croatian sawmills from different working sites (sawmilling, parquetry and sorting). A total of thirty-five floor dust samples were collected, extracted, and the mass fraction of Asp f 1 was determined using a commercially available enzyme-linked immunosorbent assay. More than 91 % of the collected dust samples had detectable levels of Asp f 1 (limit detection 3.6 ng g−1). The median Asp f 1 mass fractions in Sawmill 1 and Sawmill 2 were 49.4 ng g−1 (range
Respiratory health of wood and stone occupation workers has become a prime concern due to ceaseless exposure to the accumulation of dust results in respiratory tract infection. Review studies on the assessment of respiratory health of wood and stone occupation workers are up until now lacking, accordingly there is an urge to review such environmental health problems further. The present study emphasizes on the assessment of respiratory symptoms of wood and stone occupation workers along with recognition of associated respiratory disorders. The literature is adopted from Web of Science and Scopus database and by analyzing the abstracts and findings 38 articles have been preferred for this review. The major aim of this review is to present the key factors which are responsible for the assessment and declination of respiratory health of wood and stone occupation workers on a single platform, consequently providing the directions for upcoming research.
Wood is the raw material of the wood industry, which is used in the form of solid wood or in the processed form. Occupational exposure to wood dusts occur during processing and woodworking. The highest levels of wood dust concentrations in the work environment were recorded in the furniture and carpentry industries. The number of workers exposed to wood dust in Poland estimated during WOODEX project (2000-2003) amounted to 310 000, of which 79 000 workers were exposed to wood dust at concentrations < 0.5 mg/m3, 52 000 workers at concentrations: 0.5 ÷ 1 mg/m3, 63 000 workers at concentrations: 1 ÷ 2 mg/m3, 72 000 workers at concentrations: 2 ÷ 5 mg/m3 and 44 000 workers at concentrations > 5 mg/m3. According to data from selected sectors of the economy in Poland in the years 2001-2005, developed in collaboration with the Chief Sanitary Inspectorate at the Institute of Occupational Medicine in Łódź, the arithmetic mean value of inhaled wood dust concentrations in the wood and wood products sector (excluding furniture) was 2,08 mg/m3. This concentration was calculated on the basis of 8 602 measurements. In the case of hardwood dust, exceeded values of NDS at worksites were reported in more than 20% of the measurements, whereas in case of softwood – in less than 10% of measurements. Exposure to hardwood dust (mainly oak and beech wood) or in mixture with conifer species (softwood) is correlated with nasopharyngeal adenocarcinomas, whereas non-neoplastic respiratory symptoms, excluding asthma, are not correlated with the specific type of wood. Occupational asthma is most often the result of action of the biologically active compounds present in some wood species (both hardwood and softwood). One of the better-known species of wood and source of knowledge about occupational asthma is the dust of red cedar wood. Both dust hardwood and softwood may impair clear airway, resulting in chronic lung disease. The health effects of exposure to wood dust concern the upper or lower respiratory tract depending on the size of the wood particles. Occupational exposure to wood dust causes: chronic bronchitis, rhinitis and conjunctivitis and skin irritation, also allergic skin reactions. Spirometry has shown the reduction of the lung function index as a result of mechanical or chemical irritation of the lung tissue. It should be noted that changes in pulmonary function and the occurrence of occupational asthma was found in the woodworking industry workers, mainly employed in furniture industry (with no history of atopy) at concentrations below 1 mg / m3 of wood dust. A review of the studies in humans and in experimental animals show that wood dusts exhibit mutagenic and genotoxic effects. Analysis of DNA taken from people with cancer of the paranasal sinuses, employed in exposure to wood dusts showed mutations, mainly in the gene k-ras, which is one of the most frequently activated oncogenes in human cancers. Furthermore, h-ras mutations in adenocarcinoma patients, chromosomal aberrations in carpenter peripheral blood lymphocytes, damage to DNA strands in rats' hepatocytes, increase in micronuclear frequency in cells of mouse intestine and rats' nasal epithelium have been found. Based on results of epidemiological studies, including case-control studies showed the relationship between the incidence of the nose and paranasal sinuses cancer and the exposure to the wood dust. The risk of adenocarcinoma was a significantly higher compared to the risk of squamous cell carcinoma. The International Agency for Research on Cancer concluded that there was sufficient evidence of carcinogenicity of wood dust in humans and assigned them to Group 1 - a substances with proven carcinogenic effects in humans. The Commission of the European Union has included works related to exposure to hard and mixed wood dusts to technological processes classified as carcinogenic to humans (Directive 2004/37 / EC) and has established a BOELV value for the inhalable wood dust fraction on a level of 5 mg/m3 indicating that if there is a mixture of hardwood dust with other wood dusts then NDS refers to the total wood dust present in the mixture. SCOEL Scientific Committee resigned from the division into hard and soft wood and proposed the exposure limit value for wood dust, taking into account not only its irritating effects on upper and lower respiratory tract but also carcinogenicity (inhalable fraction: 1 mg/m3, total dust 0.5 mg/m3). The health effects of exposure to wood dust and the socio-economic conditions have alsobeen considered by the Committee on Safety and Health at Work (ACSHW), which has proposed a BOELV value for hard wood dusts of 3 mg/m3, taking into account that the lower value would result in the closure of many companies, mostly small, employing 1 to 9 employees. Establishment of the hygienic standards of wood dust is complicated by the fact that we never expose to the wood dust itself. At the same time, we are exposed to naturally occurring chemicals in wood (most of them are irritating and sensitizing). In addition, the biological fraction (bacteria, mold) found in wood dust, mainly fresh, as well as wood preservatives such as organic solvents or formaldehyde, increase the health risk. Another variable considered when assessing risk associated with exposure to wood dust is the particle size emitted during wood processing, which varies according to the type of wood and its treatment. Aerodynamic diameter of the particles is generally in the range of 10 to 30 m, which classifies them into an extra thoracic fraction (penetrating head area) or thoracic fraction (penetrating the trachea bronchial area). Percentage of respirable fraction is usually 15 ÷ 20%. When setting the NDS value for wood dusts, data from a cross-sectional survey of 161 people employed in wood dust exposure in 54 furniture companies were used. Nasal patency was examined after exposure to mixed wood dust at a low concentration (0.17 ÷ 0.74 mg/m3), mean (0.74 ÷ 1.42 mg/m3) and high (1.42 mg/m3). With regard to nasal patency before commencement of the work, exposure to medium and high concentration of wood dust significantly increased nasal congestion, reduced nasal cavity capacity and reduced nasal cross-sectional area as a result of 4-7 hours exposure. There was a statistically significant relationship between the concentration of wood dust and the nasal obstruction grade determined by the method of acoustic rhinometry and the subjective assessment. These symptoms also occurred when the dust concentrations were small, but these symptoms were not statistically significant. Furthermore, patients in the control group had significant differences in nasal passivity before commencement of work compared to the post-work period, thus undermining the observed changes at low concentrations (0.17 ÷ 0.74 mg/m3) of wood dust. Taking into account the above data as well as socioeconomic factors discussed with wood industry representatives in Poland, the Interdepartmental Commission on NDS and NDN at its 84th meeting on 4 November 2016 adopted a concentration of 3 mg/m3 for the maximum permissible concentration (NDS) for the inhalable fraction of all wood dust. Socioeconomic considerations were also taken into account in determining the BOELV value for the inhalable wood dust fraction (3 mg/m3) in the European Union. The adoption of this value without distinction for hard and soft wood is a compromise between current NDS values for wood dust with the exception of dust oak and beech (4 mg/m3) and beech and oak dust (2 mg/m3). The proposed value of NDS is at the level proposed by the European Commission for BOELV for the hard wood dust inhalable fraction (3 mg/m3), which takes into account socio-economic conditions of enterprises. Due to the fact that wood dusts have been shown to be carcinogenic, mutagenic and cause pneumoconiosis, the determination of NDSCh values is unjustified. It is proposed to mark the wood dust notation: "Carc. – category 1 carcinogen, according to the classification of the International Agency for Research on Cancer and, by reason of possible sensitization, the letter "A ".
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Air pollution by wood dust in furniture production sites is an important hygiene issue. The dust is created by all types of wood and wood-based material machining, and its concentration in the working zone surrounding the machining stand depends on the effectiveness of the dust exhaust system. In present research, three setups of the dust extraction system for a conventional table sawing machine are considered while machining particleboards. The results showed a high impact of the exhaust system connection setup on the dust concentration in the air surrounding the sawing machine work stand. The use of both main and auxiliary sawdust extraction connectors together ensured the highest clearness of the air, with only 0.5 mg/m3 of dust concentration. Closing the upper hood leads to a concentration five times higher, while disconnecting it results in a ten times higher dust content. The finest dust particles (<1 µm), however, are the most numerous in the case of closing the hood.
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Despite the implications of gender and sex differences for health risks associated with blue-collar work, adverse health outcomes among blue-collar workers has been most frequently studied among men. The present study provides a “state-of-the-field” systematic review of the empiric evidence published on blue-collar women's health. We systematically reviewed literature related to the health of blue-collar women published between January 1, 1990 and December 31, 2015. We limited our review to peer-reviewed studies published in the English language on the health or health behaviors of women who were presently working or had previously worked in a blue-collar job. Studies were eligible for inclusion regardless of the number, age, or geographic region of blue-collar women in the study sample. We retained 177 studies that considered a wide range of health outcomes in study populations from 40 different countries. Overall, these studies suggested inferior health among female blue-collar workers as compared with either blue-collar males or other women. However, we noted several methodological limitations in addition to heterogeneity in study context and design, which inhibited comparison of results across publications. Methodological limitations of the extant literature, alongside the rapidly changing nature of women in the workplace, motivate further study on the health of blue-collar women. Efforts to identify specific mechanisms by which blue-collar work predisposes women to adverse health may be particularly valuable in informing future workplace-based and policy-level interventions.
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Fungal aerosols consist of spores and fragments with diverse array of morphologies; however, the size, shape and origin of the constituents require further characterization. In this study, we characterize the profile of aerosols generated from Aspergillus fumigatus, A. versicolor, and Penicillium chrysogenum grown for 8 weeks on gypsum boards. Fungal particles were aerosolized at 12 and 20 Lmin-1 using the Fungal Spore Source Strength Tester (FSSST) and the Downloaded by [Anani Afanou] at 07:34 19 April 2015 ACCEPTED MANUSCRIPT 2 ACCEPTED MANUSCRIPT Stami particle generator (SPG). Collected particles were analyzed with FESEM. We observed spore particle fraction consisted of single spores and spore aggregates in four size categories, and a fragment fraction that contained submicronic fragments and three size categories of larger fragments. Single spores dominated the aerosols from A. fumigatus (median: 53%), while the submicronic fragment fraction was the highest in the aerosols collected from A. versicolor (median: 34%) and P. chrysogenum (median: 31%). Morphological characteristics showed near spherical particles that were only single spores, oblong particles that comprise some spore aggregates and fragments (<3.5 μm), and fiber-like particles that regroup chained spore aggregates and fragments (>3.5 μm). Further, the near spherical particles dominated the aerosols from A. fumigatus (median: 53%), while oblong particles were dominant in the aerosols from A. versicolor (68%) and P. chrysogenum (55%). Fiber-like particles represented 21% and 24% of the aerosols from A. versicolor and P. chrysogenum, respectively. This study shows that fungal particles of various size, shape and origin are aerosolized, and supports the need to include a broader range of particle types in fungal exposure assessment.
The aim of the study was to investigate occupational morbidity in the wood processing industry to gain understanding of the real situation of occupational health and to improve the diagnostics of occupational diseases. The occupational morbidity in Latvia has gradually increased from 1993 to 2004, with a slight decrease in 2005 and 2006 followed by an increase in 2007. In the year 2004, the number of first-time occupational diseases patients exceeded the number of occupational diseases patients registered in the year 1993 by 9.5, but the number of registered first-time incidences of occupational diseases in comparison with 1993 had increased by 14.5 times. In the manufacturing industry, wood and cork production, a trend of increasing rate of occupational diseases can also be observed in Latvia. A particularly rapid increase was observed in specific illnesses related to the musculoskeletal and connective tissue system, carpal tunnel syndrome as well as to occupational hearing loss, which might be explained by changes in the occupational risk factors. Despite an increase in the total number of occupational diseases in the industry of wood and cork products over the whole study period, these industries have lower levels of occupational diseases in comparison with occupational morbidity in such fields as health and social care, the extraction industry and quarry management, transportation and transport services, communications and telecommunications. In developed European Union countries, over the last few years, the number of occupational diseases has decreased, while there has been an increasing trend in Latvia. This can be explained by the fact that the working conditions in the European Union have been improving over the last few decades, and correspondingly the number of occupational diseases is decreasing. However, in Latvia, the diagnostics of the occupational diseases is rapidly improving, while improvement of working conditions has started relatively recently. Furthermore, the process has not been rapid, and therefore, results could be expected only in the future.
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Communicated by Andrejs SkaQers The aim of our study was to investigate the health condition of the emptoyed in wood processing industry, to evaluate the influence of the risk factors of the working environment on heatth of thb employed in various gender, age and working experience groups. 172 persons working in wood processing and furniture production were examined. The control group consisted of 83 office workers of the same age and length of employment. The control group had no occupationat expo-sure to wood dust and other typical wood-working risk factors. The number of totat diseases diag-nosed in employees working in wood processing was 6.3 higher than the number of diseases diagnosed in employees of the control group. The employees working in wood processing, in comparison with the persons of the control group, relatively more often suffered from chronic dis-eases of upper windpipes and bronchi, skin diseases, allergic diseases, and peripheral neruous system diseases. The employees more often than persons of the controt group suffered from de-forming vertebral spondylosis and hearing loss. Part of diagnosed diseases coutd be retated to the working conditions. The obserued spectrum and number of occupational diseases was much higher than indicated by data registered in the wood processing companies of the country.
Wood dust has been classified as a human carcinogen by the International Agency for Research on Cancer with a footnote that the evaluation was based on a marked excess of sino-nasal cancer among workers exposed primarily to hardwood dusts. Because the epidemiologic data on the carcinogenic effects of softwoods are weaker than for hardwoods, standard setting for softwood dust presents a greater dilemma. Unfortunately, the studies of wood dust and cancer do not have the quantitative exposure data necessary for standard setting for either hardwoods or softwoods. Asthma, non-asthmatic airflow obstruction, and both upper and lower respiratory symptoms have been associated with exposure to both ‘allergenic’ and ‘non-allergenic’ softwood dusts, and an association with increasing intensity of exposure has been observed in multiple studies. The available evidence seems to indicate that to prevent these nonmalignant effects, the level of exposure to all softwood dust should be at least as low 2 mg/m3. A standard of 1 mg/m3 may be more appropriate to provide a safety margin to protect more sensitive workers. It may be that some of the health effects observed are due to the natural components of wood, such as resin acids or monoterpenes, or to molds. Am. J. Ind. Med. 31:385–398, 1997. © 1997 Wiley-Liss, Inc.
Background To study respiratory symptoms in pine sawmill workers.MethodsA respiratory health questionnaire was administered to 772 pine sawmill workers and the association between symptoms and job-title-based exposure was studied.ResultsAsthma in exposed workers (18%, n = 704) was more common than in the general population (12.1%, n = 592; adjusted OR (95% CI): 1.6 (1.1–2.3)). Asthma was also more common in the low exposure group (15.6%, n = 294) and high exposure groups (high exposure to ‘green dust’; 20.4%, n = 212 and high exposure to ‘dry dust’; 18.8%, n = 198) than in the non-exposed workers (9.2%, n = 65). Adjusted odds ratios were 1.9 (0.7–4.9), 2.7 (0.9–7.6), and 2.1 (0.8–5.7), respectively. Adjusted odds ratios for symptoms of cough were 2.7 (1.2–6.5) for the low, 5.2 (2.1–13.0) for the high ‘green dust’ and 3.3 (1.4–7.9) for the high ‘dry dust’ exposure groups. Moreover, eye and nose irritations were significantly more prevalent in the high and low exposure groups.Conclusions Working in pine sawmilling is associated with an increased prevalence of asthma and cough symptoms and eye and nose irritation. Am. J. Ind. Med. 39:608–615, 2001. © 2001 Wiley-Liss, Inc.
Sumario: An epidemiological, immunological, and environmental investigation was undertaken of both current and ex-workers at the sawmill and of a control population not occupationally exposed to wood or wood products. This study has shown that exposure to wood dust at the sawmill was associated with an increased prevalence of symptoms related to nasal and conjunctival irritation and with a high prevalence of symptomatic bronchial hyper-reactivity. Sawmill workers exposed to high concentrations of dust had more work related respiratory symptoms than those exposed to lower dust concentrations and cases of extrinsic allergic alveolitis only occurred in the more heavily exposed group
Wood trimmers are exposed to molds that periodically grow on timber that may induce alveolitis and obstructive lung disease. We have evaluated respiratory symptoms, bronchial reactivity, and lung function in 28 wood trimmers at a Swedish sawmill and in 19 unexposed office workers. Eleven (sero-positive) of the wood trimmers had precipitating antibodies in peripheral blood against one or several molds. The exposure to dust (median 0.26 mg/m3), viable mold spores (median 2950 cfu/m3), viable bacteria (median 370 cfu/m3), airborne endotoxins (range 0.0015-0.0025 microgram/m3), and terpenes (range 0.4-23 mg/m3) was lower than levels that earlier have been reported to affect lung function. The wood trimmers reported an increased prevalence of cough and breathlessness. They also showed signs of a mild obstructive impairment with a tendency to increase bronchial sensitivity to metacholine and decreased FEV1 after 2 days free from exposure. FEV1 decreased more during the working week in the sero-positive workers than among the sero-negative workers, and for the whole group the decrease in FEV1 and MEF25 was correlated to the degree of mold exposure.
A voluntary scheme for the surveillance of work related and occupational respiratory disease (SWORD) was established in January 1989 with help from the British Thoracic Society and the Society of Occupational Medicine and support from the Health and Safety Executive. Three hundred and fifty four chest physicians representing 90% of the chest clinics in the United Kingdom and 361 occupational physicians submit reports regularly of newly diagnosed cases of work related respiratory illness with information on age, sex, residence, occupation, and suspected causal agent. In 1989 2101 cases were notified, of which frequent diagnoses were asthma (26%), mesothelioma (16%), pneumoconiosis (15%), benign pleural disease (11%), and allergic alveolitis (6%). Incidence rates calculated against denominators from the Labour Force Survey showed very large differences between occupational groups, especially for asthma and asbestos related diseases. Substantial regional variation in the incidence of asthma was not explained by the geographical distribution of high risk industries and was probably due to differing levels of ascertainment. The results imply that the true frequency of acute occupational respiratory disease in the United Kingdom may have been three times greater than that reported.
Workers exposed to a variety of wood dusts have been shown to exhibit occupational asthma, lung function deficits, and elevated levels of respiratory symptoms. Despite the popularity of pine and spruce, the health effects of exposures to these woods have not been extensively investigated. A study was undertaken to investigate the respiratory health of a group of sawmill workers processing pine and spruce (n = 94). Data collection included a respiratory symptom questionnaire, spirometry, and allergy skin testing. The sawmill workers were compared with a group of oil field workers from the same geographic area who underwent the same study protocol (n = 165). The results showed that the sawmill workers had significantly lower average values for FEV1 and FEV1/FVC (%), adjusted for age, height, and smoking. The largest differences were for current smokers. Significantly elevated age and smoking-adjusted odds ratios (OR) were detected for shortness of breath (2.83; 95% confidence interval [CI], 1.47 to 5.46) and wheeze with chest tightness (2.58; 95% CI, 1.18 to 5.62). Nonsignificant elevations were also seen for usual cough (1.47; 95% CI, 0.68 to 3.16), usual phlegm (1.94; 95% CI, 0.98 to 3.87), shortness of breath with exercise (1.45; 95% CI, 0.66 to 3.20), chest tightness (1.43; 95% CI, 0.80 to 2.57), and attacks of wheeze (1.70; 95% CI, 0.79 to 3.68). Sawmill workers were 2.5 times as likely as oil field workers to report current asthma (95% CI, 0.76 to 8.32). Workers employed more than 3 years showed significantly more asthma (OR = 3.67; 95% CI, 1.00 to 13.5) and bronchitis (OR = 2.14; 95% CI, 1.02 to 4.52). Sawmill workers were only 43% as likely to report a history of hay fever (95% CI, 0.20 to 0.94). These health effects were noted despite an average concentration of respirable dust of 1.35 mg/m3 (range, 0.1 to 2.2 mg/m3). These levels are below the present occupational standard.
We assessed the prevalence of occupational asthma among current (n = 29/31, 94%) and former (n = 13/49, 27%) employees of a sawmill in which eastern white cedar has been made into shingles during the past 3 yr. All participants answered a respiratory questionnaire, and all except one underwent spirometry and methacholine inhalation tests. All those with bronchial hyperresponsiveness (PC20 methacholine < or = 19 mg/ml) were invited to undergo specific inhalation challenges. Mean duration of exposure was 13 mo (19 workers > 12 mo). Twenty-eight workers (65%) reported a history compatible with asthma, and 25 (58%) had symptoms that were suggestive of occupational asthma. Only two subjects had significant airway obstruction (FEV1 < 80% pred) (mean value = 98% pred). Eighteen subjects (42%) had a PC20 < or = 16 mg/ml. Specific inhalation tests with plicatic acid and/or western red cedar (which contains twice as much plicatic acid as eastern white cedar), were done on 12 subjects who had a PC20 < or = 16 mg/ml when they were assessed. Three subjects were considered to have positive tests (one had an isolated immediate reaction, one had a late reaction, and one had significant changes in PC20 each time he was exposed but no changes in FEV1). Environmental monitoring showed concentrations of total dusts above 2 mg/m3 in half of the samples. The prevalence of occupational asthma in this workplace was three of 42 participants (7%) or at least three of 80 (3.8%) of all current or ex-workers. This is comparable to the prevalence of occupational asthma in subjects exposed to western red cedar.