Effect of Air Pollution on daily morbidity in Karachi, Pakistan.

Abstract

Levels of daily particulates (PM 2.5 ) were monitored at two sites in Karachi, Pakistan. One site (Korangi) is an industrial and residential neighborhood, while the other (Tibet Center) is a commercial and residential area near a major highway. Monitoring was done daily for a period of six weeks during spring, summer, fall and winter. Particulate levels were extraordinarily high, with the great majority of days falling into the “unhealthy for sensitive groups” or “very unhealthy” categories. The mean PM 2.5 levels in Karachi exceeded the WHO's 24 h air quality guideline almost every day and often by a factor of greater than 5-fold. Daily emergency room (ER) visits and hospital admissions for cardiovascular diseases were obtained by review of medical records at three major tertiary and specialized hospitals. ER and hospitalizations were reported relative to days in which the concentration of PM 2.5 was less than 50 μg/m ³ , and by 50 μg/m ³ increments up to 300 μg/m ³ . There were statistically significant elevations in rates of hospital admissions at each of the PM 2.5 categories at the Korangi site, and at concentrations >150 μg/m ³ at the Tibet Center site. ER visits were significantly elevated only at PM 2.5 concentrations of between 151 and 200 μg/m ³ at both sites. These results show that the extremely elevated concentrations of PM 2.5 in Karachi, Pakistan are, as expected, associated with significantly elevated rates of hospital admission, and to a lesser extent, ER visits for cardiovascular disease.

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© 2012, Khwaja, Fatmi, Malashock,
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Review article
Haider A. Khwaja,
1,2*
Zafar Fatmi,
3
Daniel Malashock,
2
Zafar Aminov,
3
Azhar Siddique,
4
and David O. Carpenter
2,5
Khwaja HA, Fatmi Z, Malashock D, Aminov Z, Siddique A, Carpenter DO. Eect of air pollution on
daily morbidity in Karachi, Pakistan, Journal of Local and Global Health Science, 2012:3 http://
dx.doi.org/10.5339/jlghs.2012.3
1.
Wadsworth Center, New York
State Department of Health,
Albany, NY
2.
Department of Environmental
Health Sciences, School of Public
Health, University at Albany,
Albany, New York, USA;
3.
Department of Community Health
Sciences, The Aga Khan University,
Karachi, Pakistan;
4.
Chemistry Department,
University of Karachi, Karachi,
Pakistan
5.
Institute for the Health and the
Environment, University at Albany,
Albany, New York, USA
*
Author for Correspondence
Haider A. Khwaja, PhD
Wadsworth Center, NYS Department
of Health
Empire State Plaza, PO Box 509
Albany, NY 12201-0509
hkhwaja@albany.edu
Eect of air pollution on daily
morbidity in Karachi, Pakistan
Abstract
Levels of daily particulates (PM2.5) were monitored at two sites in Karachi, Pakistan. One
site (Korangi) is an industrial and residential neighborhood, while the other (Tibet Center) is a
commercial and residential area near a major highway. Monitoring was done daily for a period
of six weeks during spring, summer, fall and winter. Particulate levels were extraordinarily
high, with the great majority of days falling into the “unhealthy for sensitive groups” or “very
unhealthy” categories. The mean PM2.5 levels in Karachi exceeded the WHO’s 24 hour air
quality guideline almost every day and often by a factor of greater than 5-fold. Daily emergency
room (ER) visits and hospital admissions for cardiovascular diseases were obtained by review
of medical records at three major tertiary and specialized hospitals. ER and hospitalizations
were reported relative to days in which the concentration of PM2.5 was less than 50 µg/m3,
and by 50 µg/m3 increments up to 300 µg/m3. There were statistically significant elevations
in rates of hospital admissions at each of the PM2.5 categories at the Korangi site, and at
concentrations >150 µg/m3 at the Tibet Center site. ER visits were significantly elevated only at
PM2.5 concentrations of between 151 and 200 µg/m3 at both sites. These results show that the
extremely elevated concentrations of PM2.5 in Karachi, Pakistan are, as expected, associated
with significantly elevated rates of hospital admission, and to a lesser extent, ER visits for
cardiovascular disease.
Keywords: Particulates; cardiovascular disease; respiratory disease; air monitoring; mega-city;
developing country

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Background
Ambient air pollution is a significant factor shaping public health. Recent epidemiological
studies in developed countries have highlighted an association between urban concentrations
of air pollution and health effects [1-26]. Adverse health effects of air pollution primarily include
pulmonary [27-32] and cardiovascular diseases [33-45]. Particulate matter with an aerodynamic
diameter less than 10 mm (PM10) [46-49], especially less than 2.5 mm (PM2.5) [6, 50-53], and total
suspended particulate matter (TSP) [22, 54] have been identified as major pollution factors
affecting health. The focus of research on health effects of air pollution has shifted to smaller
particles. Because of the smaller diameter, PM2.5 can be deposited deeper in the lung alveoli
where they cannot be removed by the ciliary action, a process that removes larger particulates,
and consequently have negative effects on the lung [55]. Due to the large surface area of PM2.5,
toxins (e.g., organic compounds and heavy metals) can be absorbed onto the surface. Organs
such as the lung and heart, cells, and DNA can be damaged by the toxins. The PM2.5 particles are,
therefore, regarded as being more toxic than PM10 and TSP.
Most studies investigating an association between levels of air pollution and rates of
human disease have been conducted in developed countries where concentrations of air
pollution, climatic conditions, and many other factors are significantly different from those
in most developing countries. Air pollution is a critical problem in Asian cities with possibly
serious health impact. The World Health Organization (WHO) estimates that urban air pollution
contributes each year to about 800,000 deaths and 4.6 million healthy life-years lost worldwide,
but the burden is not equally distributed: approximately 65% of the deaths and lost life-years
occur in the developing countries of Asia [56]. This disparity demonstrates an urgent need for
conducting and evaluating environmental studies on the health effects of air pollution in major
cities of Asia.
The concurrent increase in the population, industrialization, energy use, and the number
of automobiles on the roads every year is giving rise to a threatingly high rate of increase in air
pollutants in the urban areas of Pakistan (population = 173 million in 2010). A study of air pollution
levels in major urban centers found that two major cities in Pakistan have one of the highest
TSP loading recorded so far in any mega city of the world (Figure 1) [57]. Karachi, located in the
southeastern part of Pakistan on the Arabian Sea, has a population of 18 million and is one of
the most heavily polluted mega cities in the world with serious human health risks [57-59]. The
city is congested with a large number of motor vehicles (> 1.3 million). It has a large industrial base
in and around the city. Three major industrial areas, Landhi, Korangi, and Sindh Industrial Trading
Estates (SITES), are shown on the map (Figure 2). Air pollution health studies that incorporate
emergency room visits and daily admissions to hospitals are advantageous, as they make it
possible to examine the relationship between acute health outcomes and daily variations in air
pollution [19,28,34-36,39,40,60,61]. However, not a single study of the health effects of air pollution
has been performed in this developing mega city.
To respond to the call for an in-depth investigation of the health effects of ambient air
pollution in one of the largest cities of the developing world [62], we conducted a time-series
study of the effects of short-term exposure to outdoor air pollution on daily morbidity for
cardiovascular diseases. This research will provide the scientific community and policy makers
as well as the public information about the health effects of poor ambient air quality and how it
compares to other developing and developed countries of the world. The specific aim is to carry
out a long-term environmental project to investigate the association between concentrations
of PM2.5 and hospital admissions and emergency room (ER) visits for cardiovascular diseases
among residents of various communities in Karachi.

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Figure 1. Comparison of TSP Concentrations at Karachi and Islamabad with those
reported for the various megacities of the world. Reproduced with permission
from Parekh et al (2001).
Figure 2. Map of Karachi, Pakistan.
Methods
Study location. This study covered a period of 12 months (August 2008 to August 2009) and
was carried out in the city of Karachi. The study population consisted of all people who resided in
various communities in Karachi and who visited ERs and/or were admitted to two major tertiary
care hospitals serving the city [National Institute of Cardiovascular Diseases (NICVD) and Aga
Khan University Hospital (AKUH with primary diagnoses of cardiovascular diseases.
The megacity Karachi (Figure 2) is the most urbanized, industrialized, and affluent city in
Pakistan. It is located in the southeastern part of Pakistan on the Arabian Sea (Latitude 240 51'
N; Longitude 670 02' E). Most of the land consists largely of flat or rolling plains, with hills on
the north and west and an undulating plain and long coastal area in the south-east. The hills
in Karachi are the off-shoots of the Kirthar Range extending from north to south for about 300
km. The highest point of these hills is about 528 m in the extreme north of the city. The city is
comprised of 18 urban/sub-urban towns (Baldia, Bin Qasim, Gadap, Gulberg, Gulshan, Jamshed,
Kemari, Korangi, Landhi, Liaquatabad, Lyari, Malir, New Karachi, North Nazimabad, Orangi, Saddar,
Shah Faisal, and Sindh Industrial Trading Estate) and 6 cantonments, with a population of 18

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million, representing about 10% of Pakistan’s total. About 40% of the city’s population lives in low
income, non-zoned settlements and squatter colonies or “Kachi Abadis”.
Karachi’s climate is subtropical, almost desert like with scanty rainfall (mean annual
rainfall 256 mm), the bulk of which occurs during the July – August monsoon season. Pollutants
are pushed towards the shore during the northeast monsoon season and inland during the
southwest monsoons. The city is quite humid in the summer (85% humidity in August - the
wettest month) and is relatively dry in the winter (58% humidity in December - the driest month).
The average monthly temperature varies between 130C and 340C. During the summer (April
– August), the temperatures are high, ranging from 30 – 440C. Karachi has a large industrial
base in and around the city including oil-fired power plants, cement factories, steel mills, scrap
metal recycling plants, shipping, railroad yards, foundries, jute and textiles, oil refineries, heavy
petrochemical industries, automobile assembly plants, pharmaceuticals, printing and publishing
plants, food processing plants, paper mills, chemical, glass and ceramics, battery, tanneries, brick
kilns, and several light industries. There is also solid waste incineration and open burning of
municipal wastes.
Air pollution monitoring. Air pollution monitoring for PM2.5 was conducted at two fixed
stations located at Korangi (industrial/residential) and Tibet Center (commercial/residential),
located on M.A. Jinnah road in Saddar town (Figure 2) [63]. The M. A. Jinnah road is located in the
midst of a large central business district and is the main ring road in Karachi that is the busiest
road throughout the day and late evening hours. Approximately 300,000 vehicles pass M. A.
Jinnah road daily. The Korangi industrial area is the second largest industrial area of Karachi.
Approximately 2000 industries of various types are located in this area, which include refineries,
textile, chemical, and tanneries (> 100 units). The criteria for site selection included: i) location
of these stations should not be in the direct vicinity of vehicular traffic or industrial sources; ii)
locations should not be influenced by local pollution sources and should avoid buildings, trees, or
housing large emitters such as coal-, waste-, or oil-burning boilers, furnaces, flues, wood burning,
and incinerators; iii) unrestricted airflow around the sampler; and iv) sampler should be placed at
4-7 m above the ground level so that the air was relatively well mixed and less likely to be strongly
affected by sources in the immediate vicinity. Thus the PM2.5 monitoring results reflect the
general background urban air pollution level rather than local sources such as vehicular traffic or
industrial emissions.
The sampler (Figure 3) consisted of a housing, power supply, UPS as a backup, gooseneck,
5.72 cm inner diameter rubber stopper, 47 mm filter holder, data logger, mass flow meter, a pump
with a flow controller, elapsed time indicator, and a Teflon coated aluminum cyclone separator
(Model URG-2000-30EH) URG Corporation, Chapel Hill, NC, USA) with a cut size of 2.5 mm operated
at a flow rate of 16.7 L/min. PM2.5 samples for mass determination were collected on pre-weighed
47 mm 2.0 mm polytetrafluoroethylene (PTFE) membrane filters (Whatman Inc. Florham Park, NJ,
USA) with a polypropylene support ring (sequentially numbered). Sampling duration was 24 h (7:00
a.m to 7:00 a.m) at each site for 6 weeks in each quarter (i.e., January – March; April – June; July –
September; and October – December). The resulting total sampled air volume was ~ 24 m3. At the
end of each 24 h period, filters were carefully removed from the sampling device and were placed
inside the individual polyethylene petri-dishes. Graduate students under the expert supervision
of faculty members operated the monitoring sites.

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Figure 3. Schematic of the PM2.5 sampler (left) and image of sampler used in the study (right).
The laboratory for weighting PM2.5 was maintained as a “clean room” conditions to minimize
contamination, air flow interferences, and electrostatic charges. The filters, both before and after
sampling, were visually inspected for pinhole, loose material, discoloration, and non-uniformity.
They were conditioned for a minimum of 24 h in a controlled temperature/relative humidity
(RH) room to minimize the effects of water artifact (if any). The filter weights were obtained on a
microbalance (ATI CAHN, Model C-44). PM2.5 mass concentration was calculated in mg/m3 as the
difference in filter weight before and after sampling divided by the total sampled air volume.
Hospital data acquisition. Daily records of patients who visited ERs and/or were admitted
for cardiovascular diseases in NICVD and AKUH were collected. A protocol was developed for the
collection of patient’s information by trained team physicians. The data provided information
on age, gender, date of ER visit and/or admission and discharge, and the principal diagnosis
as well as demographic information. Data from AKUH was retrieved from a well-established
hospital information management system (HIMS). Our analysis focused on finding the association
between PM2.5 and daily cardiovascular hospitalizations and ER visits. It was not able to address
events that happened after admission. We reviewed the computerized records for the three
hospitals for the study period to identify all cases that were seen in ERs and/or admitted to the
hospitals for cardiovascular diseases. The causes of ER visits and/or hospital admissions were
coded according to our Classification of Cardiovascular Diseases. Prior approvals from Ethical
Review Committees of the participating hospitals and the Institutional Review Boards of the New
York State Department of Health and the University at Albany were obtained.
Meteorologic/weather variables. To allow adjustment for the effect of weather on ER visits
and hospital admissions, meteorological data (temperature - mean, maximum, and minimum
in 0C, relative humidity - mean, maximum, and minimum expressed as percentages, barometric
pressure, wind speed, and wind direction) were obtained as electronic files on a daily basis during
the sampling period from: www.wunderground.com/global/stations. All the computerized data of
PM2.5 and meteorological conditions were reviewed.
Quality control. An extensive Quality Assurance/Quality Control Program was maintained
throughout this investigation to ensure the integrity of data collected in the field. The QA/QC
plan included: detailed description of field and laboratory methods used, equipment calibration
procedures, procedures for field blanks, and storage conditions. One field filter blank check was
analyzed per batch of 10 samples. The microbalance was regularly checked with NIST-traceable
standard calibrated weights.

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The PTFE filters used for PM2.5 mass are comparatively small, each weighing ~ 150 milligrams.
Because of the size and weight of particles that are collected on these filters, net weights were
measured in micrograms. With the operational constraints of the microbalances, the introduction
of water vapor on the filters, and the measurement of small particles and filter loadings, the
weighing laboratory was designed to perform under strict operational criteria. Weights were
considered valid if duplicate weights were within 10 mg of each other.
Throughout this study, careful consideration was given to all possibilities for the
introduction of errors, either systematic or random, during each of the discrete steps that
comprise the sequence of operations, ranging from sample and hospital data collection to
data analysis. The computerized data for all the hospitals, PM2.5 results, and meteorological
conditions were reviewed thoroughly by at least two independent team members.
Statistical analysis. We created separated data records for each PM2.5 monitoring site
and hospital, including the number of ER visits per day and admissions per day, the daily
concentrations of PM2.5 , and the daily mean temperature and relative humidity. Summary
statistics were calculated for each variable including mean, standard deviation, minimum,
maximum, and percentiles. We conducted analyses on hospital data, pollutant, and
meteorological variables, stratified by location, hospital, ER visits and/or hospital admissions,
age, and gender. A generalized linear model (GLM) using negative binomial regression [28,64]
was used to conduct a time series analysis of daily counts of hospital data, daily concentrations
of PM2.5 (µg/m3), and covariates in order to estimate the influence of air pollution on ER
visits and hospital admissions due to cardiovascular diseases. In addition, data were modeled
with generalized linear Poisson model with scaled variance estimates to account for Poisson
overdispersion [61]; however, results yielded large ratio values between deviances to degree of
freedom, possibly indicating the presence of model misspecification or over dispersion. Negative
binomial regression yielded results with acceptable ratios, and consequently was chosen for final
models. Deviance and Pearson residuals were used to assess goodness of fit.
Models were adjusted for the effects of temporal trends and meteorological variables by
including the following: dummy variables for day of the week (DOW), holidays, season, cubic
splines of day (study day) with knots at the first sampling of each month, and cubic splines of
average temperature and relative humidity. Lag time between pollutant measurements and ER
visits and/or hospital admissions were evaluated using 0-, 1-, 2-, and 3-day lags for cardiovascular
diseases. Data were analyzed using the SAS statistical package (SAS Institute Inc., Cary, NC, USA;
Version 9.2).
Results and Discussion
No prior studies exist in Pakistan examining the association between levels of air pollution
with daily morbidity due to cardiovascular diseases. These preliminary results will provide
scientific community, public, and policy makers with estimates of current risks of cardiovascular
ER visits and hospitalization as a result of poor air quality. A total of 24,124 (68.6%) ER visits
and 11,023 (31.4%) hospital admissions (HAs) due to cardiovascular diseases among adults and
children living in various communities in Karachi occurred in the study period. Table 1 gives
the summary statistics for daily counts of ER visits and HAs at both sites, broken down into age
groups and by gender. Variation among the hospitals is demonstrated by the fact that the most
ER visits and hospitalizations were determined at the NICVD, which is the largest cardiac center
in the country and receives only patients with cardiovascular diseases. Overall, there were more
male hospitalizations than female. HAs were more common among males, which accounted
for approximately 58% of the total number of patients from both AKUH and NICVD (63.2% and
57.2%, respectively). Female ER visits were somewhat higher than for males However, variations
among hospitals were observed, with females comprising 39.4% and 56.6% at AKUH and NICVD,

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respectively. Men and women between the ages of 40 and 60 comprised the greatest percentage
of all HAs and ER visits.
Our hospital data indicated that the leading causes of cardiovascular disease are ischemic
heart disease (IHD, 37%), hypertension (HTN, 25%), and myocardial infarction (MI, 12%).
Cardiomyopathy (CMP, 3%) and mitral stenosis (MS, 3%) were the principal causes of ER visits and
hospital admissions in the “All Other” category. Figure 4 shows the breakdown of ER visits and
hospital admissions due to top three cardiovascular diseases by age. A persistent elevation in ER
visits and hospital admissions with age is evident. Adults between 41 and 60+ years of age were
the group seeking health care most frequently. Ischemic heart disease followed by HTN and MI
were the most common causes of admissions in this age group. ER visits due to IHD followed by
HTN and MI were more frequent in the 51-60 age groups. The percentage distribution observed in
the 41-50 or 60+ years of age and older group was slightly decreased relative to that observed for
the 51-60 years old. The lack of increased ER visits and hospital admissions in children between
0-12 years of age is not surprising, since young children are usually kept home, are less exposed
to outdoor air pollution and are less likely than older adults to suffer from cardiovascular
disease. This observation is consistent with earlier studies in developed countries by Schwartz
and Dockery [65], showing that the increased risk of deaths was greatest in the elderly, and was
greatest for cardiovascular disease. A more detailed examination of particulate matter-related
risk by deciles of age [66] showed the risk beginning to increase at approximately 40 years of age
and reaching its maximum for those 75 years of age and older.
Figure 4. Percentage of ER visits and hospital admissions according to age categories and by
leading CVDs observed during the study.

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Figure 5 shows the mean daily temperature and humidity during the study period.
Figure 5. Plots of 24-hour mean temperature and relative humidity in Karachi,
August 2008 - August 2009.
Temperature and humidity varied between 150C and 350C (mean ~ 300C except 20.40C in
the cold season) and between 24% and 88%, respectively, reflecting the subtropical climate
in Karachi. The winter season in Karachi is dominated by cold, dry air (mean humidity = 57%)
and ground-based inversion occur frequently and increases the concentration of pollutants.
Consequently, people are likely to go outdoors and are expected to have higher risks of ambient
air pollution exposure. In contrast, summer season is governed by high temperature and humidity
(mean temperature = 300C ; mean humidity = 74%), people generally use air conditioning, thus
expected to be less exposed to outdoor air pollution.
Descriptive statistics of PM2.5 concentrations and meteorological variables are presented
in Table 2. The one-year monitoring data revealed that the mass concentration of Karachi PM2.5
at the Korangi site showed a seasonal variation with higher values in winter (112 µg/m3) and
autumn (106 µg/m3), lower values in spring (94.8 µg/m3), and the lowest in summer (87.5 µg/
m3), whereas at the Tibet Center site the ranking was winter > summer > spring > autumn. Low
boundary layer heights combined with increased emissions from heating sources and biomass
burning may lead to high PM2.5 concentrations in the winter at both the sites. However, better
dispersion of pollutants caused by the increased boundary layer heights and precipitation in
summer may likely lower the PM2.5 concentrations. The same findings were also observed in the
urban area of Beijing [67], with the highest PM2.5 concentrations observed in the winter and the
lowest concentrations found in the summer.
Air quality index (AQI) is a good indicator of daily air quality and its implications for short-
term health. The higher the AQI value, the greater the level of air pollution and health risk. The AQI
was calculated [68] for PM2.5 at Korangi and Tibet Center (Figure 6), with the highest pollutant-
specific value reported as a “level of health concern” (moderate: 16 - 35 µg/m3, unhealthy for
sensitive groups: 36 - 65 µg/m3, unhealthy: 66 - 150 µg/m3, very unhealthy: 151 - 250 µg/m3, and
hazardous: 251 - 300 µg/m3). Based on the air quality index, it is evident that there were 19% days
of unhealthy air quality for sensitive groups, 67% days of unhealthy air quality, and 12% days of
very unhealthy air quality during the entire study period at Korangi site. A study by Luginaah
et al., [15] found associations between ambient air pollution and daily hospital admission of
respiratory diseases especially among females in the Windsor, Canada “area of concern”. The
mean PM10 concentration was 50.6 ± 35.5 µg/m3 and based on the air quality index, there were
165 days of poor air quality, 583 days of moderate air quality, and 1,352 days of good air quality

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during the entire study period (>2000 days). On the basis of the multi-pollutant index (MPI), Gurjar
et al., [69] report Dhaka, Beijing, Cairo, and Karachi as the most polluted, whereas Osaka-Kobe,
Tokyo, Sao Paulo, Los Angeles, New York, and Buenos Aires as the least polluted megacities.
Figure 6. Air Quality Index (AQI) at Korangi and Tiber Center in Karachi, Pakistan,
August 2008 – August 2009.
PM2.5 concentrations in Karachi are among the highest ever documented in the world. The
World Health Organization’s (WHO) 24 h air quality guideline for PM2.5 is 20 µg/m3 [70]. The mean
concentrations of PM2.5 in Karachi were in “exceedance” by a factor of at least five, implying that
airborne fine particles in Karachi have significant adverse impacts on health.
The time-series analysis showed evidence of positive associations of ambient fine particle
air pollution, meteorological factors, and seasonal parameters with ER visits and hospital
admissions due to cardiovascular diseases in Karachi. Table 3 presents the relative risk estimates
of hospital data per 50 µg/m3 in pollution. As a result of there being fewer data observed for
PM2.5 concentrations in the range 251 – 300 µg/m3, we have combined this category with PM2.5
(201 – 251 µg/m3). Note that although fine particulate air pollution was measured at two different
sites, Korangi and Tibet Center, increases in same day PM2.5 concentrations were associated with
an increase in ER visits and HAs at both sites. Statistically strongest relationships were observed
for HAs (RR = 1.613, 95% CI = 1.274 – 2.043 for Korangi; RR = 2.036, 95% CI = 1.424 – 2.911 for Tibet
Center) for PM2.5 concentrations (151 – 200 µg/m3). Unexpectedly the relations were found to
be less strong at the very highest PM2.5 concentrations –possibly residents avoid going outside
on days of extreme pollution. This analysis provides to the growing evidence linking ambient
particulate matter with daily morbidity in developing countries.
There have been a number of epidemiologic studies in developed countries that have
reported significant associations between short-term exposures to ambient particulate air
pollution and cardiovascular mortality. Studies reporting particulate matter associations with
cardiovascular hospitalizations have been more recent. Our findings complement substantial
evidence on positive associations between day-to-day variation in PM2.5 concentrations and
hospitalizations for cardiovascular diseases in developed countries. Dominici et al., [35] reported
a positive association of PM2.5 with risk for hospital admission for cardiovascular and respiratory
diseases in 204 US urban counties for 1999-2002. The largest association was for heart failure,
which had a 1.28% (95% CI, 0.78% - 1.78%) increase in risk per 10 µg/m3 increase in same-day
PM2.5 . Ito et al., [71] analyzed Medicare admission data for Detroit, Michigan for 1992-1994, along
with size fractionated particle concentration data from a nearby monitoring station in Windsor,
Ontario and showed positive associations of PM2.5 for hospitalization for ischemic heart disease,
heart failure, pneumonia, and chronic obstructive pulmonary disease (COPD). A study by Haley
et al., [36] that analyzed cardiovascular disease hospitalizations in New York State between
2001 and 2005 found the strongest association with heart failure. The increased risk (95% CI) of
hospitalizations per 10 µg/m3 increase in PM2.5 was found to be 0.46% and 1.51% for ischemic

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heart disease and heart failure, respectively. Mean concentrations of PM2.5 reported in this
study for various locations in New York State and New York City ranged from 11.1 to 15.5 µg/m3
. Relative risk estimates (95% CI) for all cardiovascular diseases from our study indicate that an
increase in PM2.5 concentrations of 10 µg/m3 at Korangi and Tibet Center is associated with an
increase in 1.6% HAs and 1.3% and 1.6% ER visits, respectively. The mean annual concentration of
PM2.5 at Korangi and Tibet Center is 100.1 and 76.6 µg/m3 , respectively. At these levels, the risk
associated with ambient particulate concentration far exceeds that which has been observed in
developed countries.
Our study has strengths and limitations. The strengths include the site of study, which is
includes the largest public hospital in the country for heart diseases serving the population of
the urban metropolitan city of Karachi. The study design and the quality of hospital data are also
major strengths. Moreover, our results are consistent with those in developed countries relating
CVD hospitalizations to exposure to particulate air pollution. Limitations of this study are the
same as in other studies of this kind. First, we assume that air pollutant concentrations measured
at fixed sites serve as a proxy for the personal exposure during the study period. Factors such
as outdoor and indoor emission sources, time spent outdoors, time spent indoors, life style, and
smoking may influence the validity of this assumption. However, personal exposure assessment
is not realistic. Second, the potential miscoding and diagnosis of CVD events may introduce a bias
in daily time-series analyses. We used only primary diagnosis, an approach that should diminish
misclassification of outcomes. Third, we monitored only HAs and ER visits and did not have
information about outpatient or physician office visits, ER visits and hospitalizations at other
hospitals. In addition, our study does not include patients with CVD who did not seek treatment,
or died at home or en-route to the hospital. We also cannot distinguish multiple hospitalizations
for one individual from those for several individuals. For these reasons our study is likely to
under-represent the true risk of ambient air pollution to the residents of Karachi. In spite of
these limitations our results provide strong evidence that significant morbidity is associated with
PM2.5 air pollution.
Conclusions
This study is one of the first to investigate the relationship between particulate air pollution
and cardiovascular diseases in a mega city in a developing country where particulate levels are
extraordinarily high. The PM2.5 levels averaging about 5 - 7 fold higher than the WHO guideline
on a “good” day, and with frequent peaks at levels as high as 279 µg/m3. Particulates were
measured at two sites, one more industrial than the other, but in general the patterns over time
were similar. Our studies show, as has been demonstrated elsewhere in developed countries,
that higher levels of PM2.5 are associated with a striking elevation in rates of ER visits and
hospitalizations for cardiovascular diseases (ischemic heart disease, hypertension, myocardial
infarction). Because of the striking levels of air pollution that we have documented, it is
imperative that further investigation of health outcomes in mega cities of developing countries
be performed.
Acknowledgements
This work was supported by Pakistan-US Science and Technology Cooperative Program
(administered by National Academy of Sciences) under the grant # PGA-7251-07-010. Authors
would like to thank Wadsworth Center, NYSDOH, University at Albany, Higher Education
Commission, Pakistan, Aga Khan University Hospital, and NICVD, Karachi and physicians who
provided and collected the health data used in this study. We owe a particular debt of gratitude
to Ms. Kelly Robbins, Drs. Vincent Dutkiewicz, Amber Sinclair, Aneeta Khoso, Sumayya Saied, Ms.
Naseem Parvez Ali, and Mr. Kamran Khan who assisted us in all aspects of this work.

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