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Assessment of chemical and bacteriological quality of pipe-borne water from various locations in Delta State University, Abraka, Nigeria



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Vol. 8(21), pp. 2137-2143, 21 May, 2014
DOI: 10.5897/AJMR12.749
Article Number: 13532A945001
ISSN 1996-0808
Copyright © 2014
Author(s) retain the copyright of this article
African Journal of Microbiology Research
Full Length Research Paper
Assessment of chemical and bacteriological quality of
pipe-borne water from various locations in Delta State
University, Abraka, Nigeria
Okoko, F. J. and Idise, O. E.*
Department of Microbiology, Delta State University, Abraka, Delta State, Nigeria.
Received 21 March, 2012; Accepted 28 April, 2014
Eighteen samples, consisting of six samples each, from three different locations that were 250, 500 and
750 away from the drinking water source in Delta State University, Abraka Campus, were collected and
analyzed for their microbial and chemical quality using standard methods. Total viable counts were
carried out using the pour plate method, while the most probable number was determined with the
multiple tube fermentation technique. The total viable counts increased with distance away from the
water source and were high for all the water samples, exceeding the 2.0 Log10cfu/ml set limit for drinking
water. The isolated organisms were Micrococcus sp., Chromobacterium sp., Streptococcus sp.,
Pseudomonas aeruginosa and Staphylocosus aureus. Chemical parameters analyzed were pH, chloride,
alkalinity, carbon-dioxide, calcium, magnesium, zinc, iron, copper, potassium, total hardness, total
dissolved solids, total suspended solids and total solids. The results obtained from each parameter
were compared with the quality standard for drinking water laid down by the World Health Organisation
and Federal Environmental Protection Agency (FEPA), Nigeria. The analyses revealed that there were
increases in some of the parameters with distance away from the water source while some of the
parameters studied were within the approved standard, others were above or below. It is thus imperative
for our drinking water to be properly treated prior to consumption.
Key words: Water, microbial, chemical, parameters, standards.
Water supply is the general process required for the
provision of water from public water system to individual
buildings and subsequent distribution of such water to
various parts of such buildings. The water from public
supply system to buildings is supplied through pipes. The
strength of the pipes, water carrying capacity, life and
*Corresponding author. E-mail: Tel: +2348136506553.
Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0
International License
2138 Afr. J. Microbiol. Res.
durability of pipes, joining process, maintenance and
repairs affect the quality of water being supplied. Piped
water remains susceptible to biological and/or chemical
contamination. Portable water supply system requires not
only pipes, but many fittings and valves which add
considerably to their functionality (Roberge, 1999).
Drinking water system thus provides habitat for
microorganisms which are sustained by organic and
inorganic nutrients present on the surface of the pipes or
in the conveyed water. Maintaining the distribution
system will require maintenance and survey procedures
to prevent contamination and also remove and prevent
the accumulation of internal deposits (Sobsey, 1989).
The safety of drinking water therefore depends on a
number of factors which include quality and source of
water, effectiveness of treatment and integrity of the
distribution system that transfer the water to containers.
The traditional approach to varying the bacteriological
and chemical safety of piped water supply has relied on
sampling strategies based on the end product, that is, tap
water (WHO, 2003; Craun et al., 1997).
The objectives of this study, therefore, are to determine
the bacteriological, and ascertain the chemical quality of
piped water distribution system and suggest ways to
reduce corrosion and increase portability of water for
human consumption.
Six samples from each of the three different locations (designated A
- C, and were 250, 500 and 750 m away from the borehole), were
collected with 500 ml sterile conical flasks, corked with cotton wool
wrapped with aluminium foil and were transported immediately to
the laboratory for analyses.
Identification of bacterial isolates
The identification of the sample microorganisms were based on
cultural, morphological and biochemical characteristics according to
the schemes of Cowan and Steel (1974), Buchanan and Gibbons
(1974) and MacFaddin (1980). The result of each test was
observed and recorded.
Bacteriological analysis
The total aerobic count (TAC) was carried out as described by Anon
(1994). The sample water was serially diluted with distilled water
after which 0.1 ml aliquots of 10-1 and 10-3 dilutions, respectively
were dispensed into separate Petri dishes. Molten plate count agar
cooled to 450°C was dispensed into each plate and incubated for
48 h at 37°C. The growths were observed and counted.
Estimation of coliforms
Coliforms were estimated using the five tube most probable number
(MPN) technique. The lauryl sulphate broth used has high nutrient
quality and the presence of phosphate buffer in this medium
enhances rapid growth and increased gas production of slowly
lactose fermenting coliform bacteria. It also inhibits the growth of
undesired bacteria. The numbers of positive tubes were compared
with MPN index table. Aliquots of the water samples were also
incubated on centrinide agar which is selective for Pseudomonas
sp. and also violet red bile which is a selective medium for
Escherichia coli. Degradation of lactose to acid is indicated by the
pH indicator, neutral red, which changes to red, and also by
precipitation of bile acids. The appearance of the colonies on the
plates is red, surrounded by reddish precipitation zones.
Chemical analyses
Determination of carbon-dioxide
Twenty millilitres (20 ml) of water sample was dispensed into a
sample vial using a sterile syringe and two drops of phenolphthalein
indicator was added. The content of the vial was mixed thoroughly
after which it was titrated with carbon dioxide reagent B (0.02 N
sodium hydroxide solution) until a pink colour was observed. The
test result was read directly from the scale on the titrator barrel and
Determination of chloride
Ten millilitres (10 ml) of water sample was dispensed into the
sample vial and three drops of chloride A reagent (5% potassium
chromate) was added as indicator and mixed thoroughly. The
mixture was titrated with chloride turned to a faint permanent brick-
red colour. The result was read directly from the scale of the
titration barrel and recorded.
Determination of alkalinity
Five millilitres (5 ml) of the water sample was pipette into the
sample vail and a tablet of BCG-MR indicator (Bromocresol green-
methyl red) was added and allowed to dissolve. The green colour
was titrated with alkalinity reagent B (0.1%) sulphuric acid0 until
solution turned purple. A post end colour was red. The result was
read and recorded.
Determination of total hardness
Three millilitres (3 ml) of the water sample was dispensed into the
vial using a syringe. The vial was inserted into the
spectrophotometer chamber and scanned blank after which it was
removed from the chamber and the sample transferred into Ca
hardness UDV (unit dose vial). The vial was mixed vigorously for
about 10 s and inserted into the chamber. The sample was
scanned and results were recorded in mg/L.
Calcium hardness
Calcium hardness was recorded as one third of the total hardness
in milligram per litre.
Magnesium hardness
Magnesium hardness was recorded as two third of the total
hardness in milligram per litre.
Determination of electrical conductivity
Electrical conductivity was determined using a conductivity meter.
The probe was dipped into a beaker containing the sample until a
stable reading was obtained and recorded in µs/cm.
Determination of pH
The pH of the water samples were determined using the Hanner
microprocessor pH meter standardized with a buffer solution of 4 to
9. The results were obtained using a stable reading.
Determination of zinc
Ten millilitres (10 ml) of the water sample was dispensed into a
clean tube with the help of a syringe. The sample was scanned
black after which 0.1 g of sodium ascorbate and 0.5 g of zinc buffer
powder were added and mixed thoroughly for 1 min. Three drops of
10% sodium cynate, 1 ml of zinc indicator solution (5.0 ml zinc
indicator solution and 17.8 ml methyl alcohol) and four drops of
formaldehyde solution (37%) were added, capped and mixed
thoroughly. The vial was inserted into the Smart spectrophotometer
and readings were recorded in mg/L.
Determination of copper
The vial was rinsed with water sample after which 3 ml of the
sample was dispensed into the vial with the help of a sterile syringe
and was capped, its content mixed thoroughly and allowed to stand
for 5 min. This was followed by further mixing to re-suspend the
settled precipitate after which it was immediately inserted into the
spectrophotometer chamber and scanned. The results were
recorded in mg/L.
Determination of cadmium
The tube was rinsed with sample water after which 10 ml of sample
was dispensed into it and scanned blank. The tube was removed
from the chamber and 1.0 ml buffered ammonia reagent, two drops
of 10% sodium citrate, 0.5 ml of PAN indicator, and 0.5 ml of
stabilizing reagent were added, capped and mixed thoroughly. The
tube was inserted into the chamber and its content scanned.
Determination of iron
The tube was rinsed with the sample water and filled to 10 ml line of
the vial and scanned blank. With the help of a syringe, 0.5 ml of iron
reagent 2 powder was added and mixed thoroughly for 30 s. The
solution was allowed to stand for 30 s for maximum colour
development after which the sample vial was inserted into the
spectrophotometer chamber and scanned. Results were read and
recorded in mg/L.
Determination of total dissolved solids
The electrode of the Hanna’s instrument (Model TDS 1) was rinsed
with distilled water after which it was dipped back into the water
sample in a clean beaker. The total dissolved solids were read by
slightly sliding the knob on top of the instrument. The result was
read and recorded.
Okoko and Idise 2139
Determination of total solids
A clean, dry and flat silica disc was weighted (W1) and 50 ml of the
water sample was dispensed into it. The content of the disc was
evaporated in a water bath. With the help of a forceps, the disc was
transferred into an oven set at 105°C for 3 h after which it was
removed, left to cool and re-weighed. The process was repeated till
a constant weight was obtained (W2). Total solid (mg/L) = (W2-W1)
20,000 mg/L.
Determination of total suspended solids
The difference between the total solids and total dissolved solids is
equal to the total suspended solids.
SS = TS - DS mg/L
The organisms isolated from the water samples
presented in Table 1 were Micrococcus sp.,
Chromobacterium sp., Streptococcus sp., Pseudomonas
aeruginosa and Staphylocosus aureus. These are
reported water resident organisms (Benka-Coker and
Olimani, 1995; Edema et al., 2006; Ukpong, 2008). Some
of the organisms are reported causal agents of some
water-borne diseases. Thus, their presence in water
could pose some effects on human health.
The results obtained in the analyses of the water
samples as presented in Table 2 shows that the mean
values of carbon-dioxide in the water samples, which
ranged from 11 - 23 ppm, were not within the World
Health Organization approved standard of 50 ppm. Hung
and Hsu (2004) reported that carbon-dioxide quickly
combines with water form carbonic acid, a weak acid.
Thus the presence of carbon-dioxide in water may have
negative effects depending on the water pH. If the water
has a high pH value, the carbonic acid will act to
neutralize it, but if the water is acidic, the carbonic acid
will act o neutralize it, but if the water is acidic, the
carbonic acid will make it even more acidic.
The mean values of chloride content, that ranged from
8.17 to 12.5 ppm, was below the 200 ppm maximum
range for standard water, and so, has no adverse health
impact when present in water for consumption and other
domestic uses.
The mean values of alkalinity of the water samples,
which ranged from 10.67 to 16 ppm, was below the set
standard of 100 ppm which would have no adverse effect
on human health while the mean values of pH, which
ranged from 5.38 to 6.32, were below the acceptable limit
of 6.5-8.5. This calls for the treatment of such water
necessary prior to consumption in order to avoid the
associated adverse health implications.
The mean values of electrical conductivity of the water
samples, that ranged from 10.32 to 31.82 µs/cm, was
2140 Afr. J. Microbiol. Res.
Table 1. Identification of bacterial isolates.
Shape Cocci in clusters Rod Cocci in chains Rod Cocci in clusters
Gram reaction + - + - +
Aerobic growth + + + + +
Anaerobic growth - + + - +
Endospore production - - - - -
Motility test - + - + -
Catalase test + + - + +
Oxidase test + + - + -
Glucose fermentation - + + - +
Organism identified Micrococcus sp Chromobacterium
sp. Streptococcus
sp. Pseudomonas
aeruginosa Staphylococcus
Table 2. Average values of water parameters of samples.
Parameter A (250 m) B (500 m) C (750 m) Set standards
CO2 8.83 11.00 23.00 50 ppm
Cl (ppm) 10.67 12.50 8.17 200
Alk (ppm) 12.00 16.00 10.67 100
Cond (µs/cm) 10.38 31.82 12.42 1000
pH 5.85 6.32 5.38 6.5 - 6.8
Hardness (ppm) 21.83 27.83 21.00 100
TDS (ppm) 0.57 1.92 0.80 -
TSS (ppm) 0.22 0.50 0.16 -
TS (ppm) 0.79 2.42 0.96 500
Mn (ppm) 14.55 17.55 14.00 30
Ca (ppm) 7.25 8.77 7.00 75
Zn (ppm) 0.09 0.10 0.18 5.0
Cu (ppm) 0.23 0.27 2.25 1.0*
K (ppm) 0.24 0.63 0.63 10.00
Cd (ppm) 0.09 0.07 0.23 0.003*
Fe (ppm) 3.63 1.38 1.66 0.30*
Total aerobic counts 2.35 2.67 3.56 -
Coliforms (cfu/ml) 0.33 2.33 1.33 0.00*
* = Above set limits.
within the acceptable limit of 10.00 µs/cm set by the
World Health Organisation and Nigeria for drinking water. The showed that the mean values of total solids
present in the water samples were within the acceptable
range of 500 ppm. Storey and Ashbolt (2003b) reported
that solids can either be suspended or dissolved solids
and together are referred to as total solids. Solids in
water samples can vary significantly with season and
rainfall. Events and abnormal changes in the amount and
type of solids, whether total or dissolved can provide
information on the pollution level of the water. Solids can
also affect the taste and appearance of the drinking
The mean values of zinc concentration, which ranged
from 0.09 to 0.18 ppm, were within the set limit of 5 ppm.
While the copper concentration of the samples from
locations A (0.23 ppm) and B (0.27ppm) were within set
limits, water samples from Location C (2.25 ppm) was
above the acceptable limit of 1.0 ppm.
The mean values of value for potassium concentration,
which ranged from 0.24 to 0.63 ppm, were within the
acceptable standard of 1.0 ppm. However, the mean
values of values for cadmium (0.09 – 0.23 ppm) and iron
(1.38 – 3.63 ppm) were above the set limits of 0.003 and
0.30 ppm, respectively. Florea and Busselberg (2006)
and Hung and Hsu (2004) reported that some trace
elements are potentially toxic. Zinc and copper are
essential elements for the maintenance of the body’s
metabolic activities but copper contaminated water could
pose health hazards such as abdominal pains, nausea,
vomiting, diarrhoea, headache and dizziness as reported
by Chinwe et al. (2010). Copper poisoning principally
influences formation of liver cirrhosis known as non-India
childhood cirrhosis (WHO, 2003). Jerup (2003) reported
that some trace elements are potentially toxic because
they act on the cell membrane or interfere with the
cytoplasmic or nuclear functions when they enter into the
cell, hence their entry into the human body could result in
malfunctioning of the body systems. Therefore copper,
zinc, cadmium and other trace metals have adverse
effects in humans if present in water samples in very high
concentration. Cadmium, for instance, derives its
toxicological properties from its similarity with zinc, an
essential micronutrient in humans. Cadmium is bio-
persistent and once absorbed by humans, remains
resident for many years, although it is eventually
The mean values of total aerobic counts (2.35 –
3.56Log10cfu/ml) of the water samples were high.
According to the World Health Organization (2003)
report, a high aerobic count does not itself present a risk
to human water supply system. A particular feature of the
Pseudomonas aeruginosa is its ability to grow in low
nutrient water. Warburton (1992) reported that the
Pseudomonas strains present in water usually do not
have the same genetic pattern as those in clinical cases
during gastrointestinal infections. Though, Allen et al.
(2000) reported that water for human consumption is
required to be free from any bacteria that may pose a
health risk, the presence of Pseudomonas in these water
samples may not pose adverse health hazard due to their
genetic constitution.
The presence of biofilms in the drinking water
distribution system may play a role in the presence of
potential pathogens in drinking water pipes. This
contamination can occur due to defective joints, back
siphonage, rusted pipelines crossing over the sewage
pipes and low/high pressure in the pipelines. For water to
be wholesome, it should not present a risk of infection or
contain unacceptable contamination of chemicals
hazardous to health and should be aesthetically be
acceptable to consumers.
The mean values of coliform counts (0.33 -
2.33log10cfu/ml) were higher than the set standard of 0.0.
This could have been due to mixing-up of water and
sewage where the water pipes are broken. Being
indicator organisms of faecal contamination and the
causal organisms of many water-borne diseases, it is
Okoko and Idise 2141
therefore pertinent to treat the water with physical and/or
chemical methods prior to use for domestic uses. The
university community draws her drinking water from
these locations and this could lead to outbreak of
water-borne infections if treatment options are not
The Pearson moment correlation coefficients presented
in Table 3 revealed strong correlations between the
tested parameters. CO2 was strongly correlated to Zn,
Co, K, Cd and TAC; Cl was strongly correlated to
alkalinity, conductivity, pH, Mn, Co, hardness, TDS, TSS
and TS; Alkalinity was strongly correlated to pH, Mn, Ca,
hardness, TDS, TSS, TS, Cl and coliform counts;
conductivity was strongly correlated to Cl, alkalinity, Mn,
Ca, hardness, TDS, TSS, TS and K; pH was strongly
correlated to Cl, alkalinity, conductivity, Mn, Co,
hardness, TDS, TSS and TS; Mn was strongly correlated
to Cl, alkalinity, conductivity, pH, hardness, TDS, TSS,
TS and coliform counts; Ca was strongly correlated to Cl,
alkalinity, conductivity, pH, Mn, TDS, TSS. TS and
coliform counts; Hardness was strongly correlated to Cl,
alkalinity, conductivity, pH, Mn, Ca, TDS, TSS, TS and
coliform counts; TDS, TSS and TS were strongly
correlated to Cl, alkalinity, conductivity, pH, Mn, Ca,
hardness and coliform counts; TDS was strongly
correlated to TSS and TS; Zn was strongly correlated to
CO2, K and total aerobic counts; Cu was strongly
correlated to CO2, K, Cd and total aerobic counts; K was
strongly correlated to CO2, conductivity, TDS, TS, Zn, Cu,
total aerobic counts and coliform counts; Cd was strongly
correlated to CO2, Cu and total aerobic counts; Fe was
not correlated to all parameters; TAC was strongly
correlated to CO2, Zn, Cu, K and Cd while CC was
strongly correlated to alkalinity, Mn, Ca, hardness, TDS,
TSS and TS and K.
Student t-test at 95% confidence level revealed that
there was a statistically significant difference between the
values in the locations. The parameters increased with
distance away from the water source (borehole).
The need for suitable water for human consumption can
never be overemphasized. The water parameters were
found to vary with distance away from the water source.
There is need to maintain water quality during transport
either by chemical and/or physical treatments to avert
water related diseases which are harmful to the health of
Conflict of Interests
The author(s) have not declared any conflict of interests.
2142 Afr. J. Microbiol. Res.
Table 3. Pearson moment correlation coefficient for the tested parameters.
Parameter CO2 Cl
(ppm) Alk
(ppm) Cond
(µs/cm) pH Mn
(ppm) Ca
(ppm) Hardness
(ppm) TDS
CO2 1
Cl (ppm) -0.83802 1
Alk (ppm) -0.58349 0.932098 1
Cond (µs/cm) -0.29041 0.765485 0.94657 1
pH -0.78615 0.996033 0.96063 0.819704 1
Mn (ppm) -0.50154 0.89235 0.995237 0.9735 0.928971 1
Ca (ppm) -0.48976 0.886146 0.993823 0.976512 0.923865 0.999908 1
Hardness (ppm) -0.47286 0.877048 0.9915 0.980484 0.916316 0.999461 0.999814 1
TDS (ppm) -0.21925 0.716095 0.920292 0.997292 0.775364 0.954047 0.958023 0.963372 1
TSS (ppm) -0.52015 0.90191 0.997114 0.968322 0.936766 0.999766 0.99938 0.998516 0.947337
TS (ppm) -0.28207 0.759858 0.943728 0.999962 0.81469 0.971473 0.9746 0.978736 0.997895
Zn (ppm) 0.999155 -0.85974 -0.61637 -0.32949 -0.81088 -0.53667 -0.52518 -0.50868 -0.25916
Cu (ppm) 0.992157 -0.89965 -0.68043 -0.40774 -0.85724 -0.60575 -0.5949 -0.5793 -0.33949
K (ppm) 0.618038 -0.08898 0.27783 0.572787 5.25E-16 0.370151 0.382718 0.400456 0.631515
Cd (ppm) 0.967003 -0.94938 -0.77114 -0.52461 -0.91766 -0.7054 -0.69572 -0.68174 -0.46058
Fe (ppm) -0.52424 -0.02532 -0.38569 -0.66263 -0.11417 -0.47379 -0.48569 -0.50245 -0.71591
Total aerobic counts 0.993349 -0.76962 -0.48609 -0.17829 -0.70976 -0.39859 -0.38611 -0.36826 -0.10545
Coliforms (cfu/ml) 0.142162 0.420956 0.720923 0.9059 0.5 0.785046 0.793376 0.804963 0.93459
Table 3. contd.
Parameter TSS
(ppm) TS
(ppm) Zn
(ppm) Cu
(ppm) K
(ppm) Cd
(ppm) Fe
TSS (ppm) 1 1
TS (ppm) 0.966112 0.966112 1
Zn (ppm) -0.55481 -0.55481 -0.32126 1
Cu (ppm) -0.62283 -0.62283 -0.39978 0.996456 1
K (ppm) 0.349957 0.349957 0.579897 0.585206 0.514923 1
Cd (ppm) -0.72058 -0.72058 -0.51718 0.976656 0.991264 0.39736 1
Fe (ppm) -0.45462 -0.45462 -0.66912 -0.4888 -0.41368 -0.99346 -0.28999 1
Total aerobic counts -0.41835 -0.41835 -0.16972 0.987777 0.971165 0.704449 0.931235 -0.61881 1
Coliforms (cfu/ml) 0.771454 0.771454 0.909551 0.101361 0.017318 0.866025 -0.11471 -0.91745 0.255193
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Metals and metal compounds are constituents of our natural environment. Their distribution depends on the existence of natural sources (e.g. volcanoes or erosion) and their use in human's activity. They are transformed naturally (e.g. by bacterial activity) with formation of organic species that influence their mobility and accumulation in abiotic as well as biotic systems. Up to date metal species are released into the environment questioning their influence on human health. Due to their widespread use in human activities such as industry, agriculture and even as medicine (e.g. As, Se, Pt), numerous health risks may be associated with exposure to these substances. Different reports on metal intoxication are documented and studies especially on neurotoxicity, genotoxicity, or carcinogenicity, are previously published in numerous articles. This mini-review gives an overview on the use and the actions of selected metal species of actual scientific concern, with a focus on neuronal cells.
The recent literature on disinfection of health-related microorganisms in water and wastewater is reviewed. There is now considerable evidence that traditional microbial indicators of water and wastewater quality, such as total and fecal coliform bacteria, are inadequate to predict the presence or disinfection responses of several important, newly recognized bacterial, viral and protozoan pathogens. This review emphasizes the response to disinfection of waterborne microbial pathogens and potential indicators of recent recognition and public health concern. These organisms include heterotrophic plate count (HPC) bacteria, frank and opportunistic bacterial pathogens, such as Campylobacter jejuni, Yersinia enterocolytica, non-tubercular mycobacteria, Legionella spp. and pseudomonads; coliphage indicators and enteric viral pathogens, such as hepatitis A virus, rotaviruses and Norwalk virus; and protozoan pathogens, such as Giardia lamblia, Cryptosporidium, and the free-living amoeba (e.g., Acanthamoeba spp. and Negleria spp.). The responses of these organisms to widely used, traditional disinfectants, such as free and combined chlorine, and to disinfectants of more recent interest, such as ozone, chlorine dioxide and ultraviolet light, are reviewed. This review also attempts to identify the variety of factors influencing disinfection efficiency, especially those that interfere with disinfection. It is apparent that traditional microbial indicators, such as total and fecal coliforms, are more sensitive to disinfection than such pathogens of recent concern as mycobacteria, enteric viruses and protozoan cysts. Therefore, efforts must be continued to find more reliable indicators of disinfection efficiency and microbial water quality and improved methods for water and wastewater disinfection.
The main threats to human health from heavy metals are associated with exposure to lead, cadmium, mercury and arsenic. These metals have been extensively studied and their effects on human health regularly reviewed by international bodies such as the WHO. Heavy metals have been used by humans for thousands of years. Although several adverse health effects of heavy metals have been known for a long time, exposure to heavy metals continues, and is even increasing in some parts of the world, in particular in less developed countries, though emissions have declined in most developed countries over the last 100 years. Cadmium compounds are currently mainly used in re-chargeable nickel-cadmium batteries. Cadmium emissions have increased dramatically during the 20th century, one reason being that cadmium-containing products are rarely re-cycled, but often dumped together with household waste. Cigarette smoking is a major source of cadmium exposure. In non-smokers, food is the most important source of cadmium exposure. Recent data indicate that adverse health effects of cadmium exposure may occur at lower exposure levels than previously anticipated, primarily in the form of kidney damage but possibly also bone effects and fractures. Many individuals in Europe already exceed these exposure levels and the margin is very narrow for large groups. Therefore, measures should be taken to reduce cadmium exposure in the general population in order to minimize the risk of adverse health effects. The general population is primarily exposed to mercury via food, fish being a major source of methyl mercury exposure, and dental amalgam. The general population does not face a significant health risk from methyl mercury, although certain groups with high fish consumption may attain blood levels associated with a low risk of neurological damage to adults. Since there is a risk to the fetus in particular, pregnant women should avoid a high intake of certain fish, such as shark, swordfish and tuna; fish (such as pike, walleye and bass) taken from polluted fresh waters should especially be avoided. There has been a debate on the safety of dental amalgams and claims have been made that mercury from amalgam may cause a variety of diseases. However, there are no studies so far that have been able to show any associations between amalgam fillings and ill health. The general population is exposed to lead from air and food in roughly equal proportions. During the last century, lead emissions to ambient air have caused considerable pollution, mainly due to lead emissions from petrol. Children are particularly susceptible to lead exposure due to high gastrointestinal uptake and the permeable blood-brain barrier. Blood levels in children should be reduced below the levels so far considered acceptable, recent data indicating that there may be neurotoxic effects of lead at lower levels of exposure than previously anticipated. Although lead in petrol has dramatically decreased over the last decades, thereby reducing environmental exposure, phasing out any remaining uses of lead additives in motor fuels should be encouraged. The use of lead-based paints should be abandoned, and lead should not be used in food containers. In particular, the public should be aware of glazed food containers, which may leach lead into food. Exposure to arsenic is mainly via intake of food and drinking water, food being the most important source in most populations. Long-term exposure to arsenic in drinking-water is mainly related to increased risks of skin cancer, but also some other cancers, as well as other skin lesions such as hyperkeratosis and pigmentation changes. Occupational exposure to arsenic, primarily by inhalation, is causally associated with lung cancer. Clear exposure-response relationships and high risks have been observed.
The authors evaluate the utility of coliforms as an indicator of the vulnerability of drinking water systems to outbreaks of waterborne disease. Coliform‐free tap water has previously been thought to be unlikely to cause waterborne disease. However, disease outbreaks (especially those caused by Giardia or Cryptosporidium ) and endemic waterborne disease risks have been reported in water systems that have not violated either the 1975 or 1989 maximum contaminant level (MCL) for total coliforms. Focusing on the 1975 rule and using coliform data and investigative reports about outbreaks, the authors compared MCL violations for water systems that did and did not experience an outbreak. Coliforms were usually found in a public system during an outbreak investigation, but in the months before an outbreak, they were detected in only half of the systems and caused an MCL violation in only one fourth of them. The violation rate was not significantly different between community systems that experienced an outbreak and those that did not; usually both met the MCL. To safeguard the public against waterborne disease, microbiological monitoring must be supplemented with periodic sanitary surveys and activities that ensure adequate water quality.
Through their many sorption sites, microbial biofilms can accumulate both organic and inorganic particulate and colloidal material from bulk water environments. An application of such first principles to the ecology of "biocolloidal" enteric virions would suggest that they too may be concentrated by biofilms in a similar way. Though previous studies have isolated human gastrointestinal (enteric) virions from microbial biofilms, the exact human health significance of this has been neither fully investigated nor completely understood. Through an assessment of the location, accumulation and persistence of model enteric virion (phiX174, MS2 and B40-8 bacteriophages as well as 20 nm fluorescent latex microspheres) within biofilms, the aim of the current study was to investigate whether the interaction of enteric virions with distribution pipe biofilms could provide a secondary source of public health concern to consumers. Model enteric virions were found to be incorporated into biofilms at concentrations representing 1% of those present in the adjacent bulk water environment. A sub-population (0.01%) of these persisted throughout an experimental period of 30 days, inferring their potential to accumulate over time. Furthermore, model enteric virions were partitioned into bacterial microcolonies, environments where biofilm bacteria can persist and re-grow, even in the presence of "acceptable" levels of disinfection. A risk model for enteric virion accumulation and release from distribution pipe biofilms suggested that associated risks may exceed USEPA benchmark values. These findings could have wide-reaching implications in water treatment and distribution strategies, and necessitate a re-appraisal of current water guideline values.
Surface and gravity-cored sediments were collected from the Kaoping coastal area off southwestern Taiwan to determine particle size, organic carbon, trace metal concentration and enrichment factor (EF), 210Pb dating, and 206Pb/207Pb ratio for determining present and historical metal pollution. Surface distributions of trace metals ranged from 0.02 to 0.13 mg/kg for Cd (EF: 0.16-1.65), from 35 to 189 mg/kg for Cr (EF: 0.85-2.92), from 25 to 64 mg/kg for Ni (EF: 0.53-2.38), from 10 to 32 mg/kg for Pb (EF: 1.20-4.94), and from 29 to 129 mg/kg for Zn (EF: 1.18-3.50). Trace metal concentrations correlate closely with distributions of mud (<63 microm) and organic carbon which accumulate largely around river mouths and within the Kaoping Canyon. With the exception of Cd, Cr and Ni in certain areas with rather coarse sediments, metals were generally elevated above the baseline levels over the studied area. Metals were also relatively enriched in areas with high contents of mud and organic carbon. Sedimentation rates derived from the excess 210Pb data in core sediments sampled from the canyon illustrate metal pollution beginning around 1970 that is corresponding to the booming time of economic growth in Taiwan. Meanwhile, the status of Pb pollution in core sediments is verified by an inversed correlation between 206Pb/207Pb ratios and Pb concentrations. Anthropogenic Pb and other metals in the studied area were apparently derived primarily from the Kaoping River and accumulated around the river mouth and within the Kaoping Canyon. The Kaoping Canyon appears to act as a major sink for river borne trace metals.