HS 17 - Literature

This paper describes the study previously reported in Health Stream (Issue 12). The relative bioavailabilities of aluminium (Al) in food and in municipal alum-treated drinking water were determined by measuring Al uptake into blood plasma, and Al excretion in urine of volunteers. It was found that the bioavailability of Al from water (0.37 percent) was similar to that of food (0.28-0.64 percent), which confirms that Al from drinking water is not more easily absorbed than Al from food. Therefore Al from drinking water was not likely to contribute to the incidence of Alzheimer’s disease. It was also estimated that drinking 1.6L/d of ATW containing 140 microgram/L Al would only contribute 0.4-1.1 percent of the lifetime body burden of Al.

In our last issue we summarised a paper by Altmann et al. on a study of cerebral function in people resident in Camelford UK when the drinking water supply was contaminated with high levels of aluminium sulphate. We were unable to locate information on the potential exposure levels during this incident.

The report of Lowermoor Incident Health Advisory Group (Chaired by Prof Dame Barbara Clayton) published in July 1989 gives information on water quality. Para 6 states that "As a result of the Lowermoor incident, it is likely that for a period of up to three days consumers were supplied with acidic water of pH as low as 3.9-5.0. An aluminium content of up to 620 milligrammes per litre and a sulphate concentration of up to 4500 milligrammes per litre were recorded." The report goes on to say that "The level of aluminium fell below 1 milligramme per litre in the second phase of the incident, but the EC MAC of 0.2 milligrammes per litre was only achieved after a period of intensive cleaning and flushing".

This study examined whether the excretion of arsenic in urine is a biomarker for exposure to inorganic arsenic (InAs) in drinking water. Subjects were recruited from residents of Millard County, Utah who had not changed their place of residence in the last 5 years. Half of the subject were residents in a town supplied by well water with low InAs concentration (less than 20 microgram/L). The rest of the subjects lived in surrounding areas with higher concentrations of InAs in well water (more than 20 microgram/L). Each subject completed an exposure assessment questionnaire and answered questions regarding demographics, medical history, and length of residence in their present home as well as use of drugs, alcohol, or tobacco and daily water consumption. A diet diary was kept for 6 consecutive days and arsenic intake from drinking water estimated.

Males comprised 56% of subjects, and 44% of subjects were younger than 18 years. Ninety-six study subjects provided first morning void urine samples for 5 consecutive days. On one of the days a 24-hr urine collection was done. Tap water samples were collected in the homes of subjects and analysed for InAs. Concentrations of InAs in the home drinking water ranged from 8 to 620 microgram/L.

The concentrations of As in urine were found to be stable throughout the day. There was also very little individual day-to-day variation in As concentration in urine. Urine concentration did not vary by gender, however an age dependent difference was seen. Concentrations of As in drinking water were a better predictor of the concentration of As in urine than the estimated intake of As from drinking water. The authors suggest that repeated urine samples may not be needed to give good estimates of InAs exposure, and measurement of InAs in drinking water may be a useful substitute for estimating individual exposure. The subjects may have reached a "steady state" of arsenic intake and excretion due to continuous exposure.

Comment Participants in this study were members of the Mormon Church and did not consume alcohol or caffeine, and were non-smokers. The observations in this population may not be applicable to the broader community as both alcohol and caffeine affect urinary output.

This paper reviews the contamination of groundwater with arsenic in Bangladesh by examining the tubewell (bore well) contamination and the related health impacts. Records from over 30,000 tubewell samples were analysed. Arsenic levels exceeded the WHO guideline value for drinking water of 0.01 mg/l in 55 of the 64 districts of Bangladesh. In 52 districts the arsenic contamination in several wells was considerably above the Bangladesh drinking water standard of 0.05 mg/l. Among the 52 districts, 17 had maximum arsenic levels in groundwater exceeding 1 mg/l.

The affected districts are mainly crop producing areas where most residents are involved in manual agricultural labour, and average daily water intake for adults has been estimated at 5-6 litres. Additional arsenic is also consumed in food prepared with contaminated water. Despite a high prevalence of arsenic related skin lesions and other illnesses, public awareness of the hazard is low.

This ecological study was undertaken to investigate associations between cancer incidence and drinking water contamination with atrazine and/or nitrate, and related agricultural practices in the Ontario agroecosystems for the years 1987-1991. Both nitrate and atrazine are chemicals used in modern agriculture and have contaminated groundwater in the Ontario agroecosystem. Some epidemiological studies have suggested possible associations between these two chemicals and certain cancers.

Cancer data was obtained from the Ontario Cancer Registry for cancer of the stomach, colon, ovary, bladder and central nervous system and non-Hodgkin’s lymphoma. The cancer data was aggregated into 40 ecodistricts. Cancer incidence rates were calculated by dividing the number of new cases of cancers in each ecodistrict during 1987-1991 by the number of person-years of population-at-risk during this time period. The cancer incidence rates were age standardised using sex-specific 5-year age groups. Data on water contamination, and agricultural practices in each district was obtained from government surveillance programs. Average values for confounding variables such as alcohol consumption, smoking, education level, income, and occupational exposures were estimated from census and health survey data.

The atrazine contamination levels ranged from 50-649 ng/l, the maximum acceptable concentration (MAC) being 60,000 ng/l. Atrazine was significantly associated (p<0.05) with increased stomach cancer incidence and decreased colon cancer incidence in both males and females. Atrazine levels appeared to have reduced the colon cancer incidence, although there is no known biological reason for such an effect. The authors suggest there may be interaction between social and biological variables such as higher vegetable production and consumption in areas with higher atrazine use.

The nitrate contamination levels ranged from 0-91 mg/l with the MAC of 10 mg/l. Nitrate was negatively associated with stomach cancer incidence in males and females. This result is in contradiction to other studies, which have found positive associations or correlations with drinking water nitrate levels and stomach cancer. These earlier studies however, did not consider the possible interactions or complex feedback loops, which occur in an agroecosystem.

Comment This study is limited by the fact that the individual exposure levels of people with and without cancer were not examined, and individual confounding factors (smoking, diet) were also not determined. The time frame of exposure measurement is also not appropriate - exposure levels for ecodistricts were estimated from levels of atrazine and nitrate measured in water during 1991/1992, and pesticide and fertiliser use from surveys during 1983 to 1988. However the cancers examined here were diagnosed between 1987 and 1991, and could not have been attributable to such recent exposures. Exposure data for 10 to 30 years prior to diagnosis would be more relevant for these cancers.

This ecological study analysed the difference between trace elements in drinking water collected from areas with high incidence and low incidence of gastric carcinoma. Drinking water samples were collected from Shewopo town in Qixia county in China where mortality from gastric carcinoma is high and from Shenshan town in Cangshan county where mortality is low.

The concentration of titanium (Ti), vanadium (V), iron (Fe), copper (Cu) and strontium (Sr) were significantly higher in the drinking water from the high cancer incidence county. However, the concentration of arsenic (As) was significantly higher in the low cancer incidence county.

The authors comment that there have been no previous reports of an association between V and cancer, and few reports that Ti and Sr are correlated positively with cancers. However a number of studies have reported a correlation between high levels of Fe and Cu in drinking water and cancer incidence.

The aim of this study was to examine the relationship between the total hardness levels in drinking water from municipal supplies and death from esophageal cancer. The hardness of drinking water is mainly determined by its calcium and magnesium content.

A total of 322 municipalities in Taiwan were analysed. The Bureau of Vital Statistics of the Taiwan Provincial Department of Health provided data on all deaths of Taiwan residents from 1987 to 1996. A case group was formed consisting of all eligible esophageal cancer deaths occurring in people between 50 and 69 years. A control group consisted of all other deaths caused by malignant neoplasms of stomach, colon, rectum, rectosigmoid junction and anus and pancreas. Control subjects were randomly pair matched to the cases by sex, year of birth and year of death. The Taiwan Water Supply Corporation provided information on the total hardness of each municipality’s drinking water. The source of cases and controls hardness exposure via drinking water was assumed to be their municipality of residence, this was identified from death certificates.

A total of 2084 cases and 2084 controls with complete records were included in the study. The percentage of cases and controls with hard water (over 150mg/L) was 38.3% and 42.3% respectively, moderately hard water (between 75 and 150mg/L) 28.8% and 33.2% respectively and soft water (less than 75mg/L) 32.9% and 24.5%. Odds ratios and 95% Confidence Interval for esophageal cancer relative to individuals who had hard water were 0.96 (95% CI=0.82 1.09) for people who lived in places served by moderately hard water and 1.42 (95% CI= 1.22 1.66) for people who had soft water.

A significant increasing trend in the odds ratios for esophageal cancer with decreasing levels of hardness was found. The results suggest that hard water seems may have a protective effect against esophageal cancer, however further studies are required to investigate the water intake of individuals, and confounding factors such as tobacco and alcohol consumption.

This article reviews the toxicological and epidemiological evidence for an association between disinfection byproducts (DBPs) and adverse reproductive outcomes. The formation of DBPs is briefly described, and it is noted that the trihalomethanes are usually the most abundant byproducts of water chlorination. Several other classes of DBP compounds are also formed, but these are less commonly monitored.

Experiments in laboratory animals (mostly rodents) have shown that exposure to high levels of some DBPs can cause reproductive or developmental toxicity. In these experiments exposure levels have ranged from 10,000-fold to greater than a million-fold higher than the levels normally found in drinking water. In addition, DBPs have generally been administered to test animals as a single daily dose by gavage, rather than being consumed over the course of a day. In most studies the observed effects appear to be due to generalised toxicity (eg reduced foetal body weight), but in some instances foetal malformations have been observed. A number of animal studies have also reported adverse effects on male and female fertility. The biological mechanisms by which DBPs affect reproduction or foetal development are not well understood, and a number of DBPs have not yet been studied for such effects.

Ten epidemiological studies on DBPs and human reproductive outcomes published between 1992 and 1999 are summarised. The authors excluded 4 papers relating to Santa Clara County in California where contamination of groundwater by trichloroethane (not a DBP) has been associated with increased risks of spontaneous abortion and congenital anomalies.

A wide range of reproductive outcomes have been studied including spontaneous abortion, stillbirth, low birthweight, intra-uterine growth retardation, preterm delivery and a range of congenital malformations. Some studies have shown statistically significant increases in risks for some adverse outcomes but no consistent pattern is evident across studies. In most cases, confidence intervals have been wide and dose-response trends were not seen.

Comparison of the studies is difficult because of the different exposure indices and outcome measures used. In three studies exposure to different levels of DBPs was inferred from the mothers residence at time of delivery, and the type of water source (surface water vs groundwater) or the type of water treatment (chlorinated vs chloraminated vs undisinfected). Four studies have used the mothers residence plus routine THM measurements by water companies as an index of exposure, however in one instance the water measurements were done two years prior to the pregnancies under study. Only three studies have used individual interviews or questionnaires to estimate water intake by women, and two of these also included estimates of exposure to volatile DBPs through showering or swimming. Even in these cases, the exposure levels were inferred from measurements taken by the water company at 3 monthly intervals at a few sites in the water distribution system.

Overall, the available evidence suggests the risks, if any, are small, but the issue is still important because of the large exposed population. Shortcomings in studies carried out to date are discussed and recommendations for future studies are made, including:

The authors conclude that further well designed epidemiological studies on reproductive outcomes and male fertility are needed, but also note that such studies will remain relatively crude until improved exposure assessment for DBPs is employed.

The objective of this study was to examine whether current water treatment is sufficient to prevent all waterborne illness in the City of Le Havre, France. Records from two water treatment plants were compared with pharmacy sales records of anti-diarrheal and gastrointestinal medication to determine whether an association existed between levels of community gastroenteritis and changes in water quality parameters.

One water treatment plant (Radicatel) uses direct sand filtration prior to chlorination and also uses coagulation- setting when raw water turbidity exceeds 3 NTU (20% of time). The other plant (Saint-Laurent) uses only chlorination, and supplies consumers only when raw water turbidity is below 1.5NTU. The plants are continuously monitored for turbidity and free chlorine. Both plants extract water from a chalk aquifier, but the Radicatel source is frequently subject to the influence of surface water. The aquifier is subject to pollution from surface runoff and seepage.

An ecological time series approach was used for data collected between April 1993 and September 1996. Medication sales data from 3 pharmacies, residual chlorine and turbidity measurements were all analysed. Chlorine was detectable at the Radicatel site throughout the study period although barely detectable on 9 occasion. Failures of the chlorination process occurred on 13 occasions at the Saint-Laurent site with treated water containing no detectable chlorine.

A correlation was found between low or absent disinfection levels at the Saint-Laurent plant and an increase in medication sales. No such correlation was seen for the Radicatel plant. No correlation was seen between medication sales and changes in finished water turbidity from either plant, however an association was found between increases in raw water turbidity at the Radicatel plant and medication sales. The authors note that faecal indicator organisms (faecal coliforms and streptococci) were absent from treated water samples, but treated water turbidity occasionally reached relatively high values (4.9 NTU for Saint-Laurent and 3.0 NTU for Radicatel).

There was a delay of 3 to 8 days between chlorination failures at Saint-Laurent and increase in medication sales. A delay of 1 to 3 weeks was found between raw water turbidity increases at Radicatel and increased medication sales. The authors estimate that the overall rate of gastroenteritis from all sources was about 0.35 episodes /person /year, and that perhaps 0.02 episodes /person /year (about 10%) may be due to intermittent problems with drinking water quality.

Comment The observations reported in this paper support the hypothesis that some fraction of community gastroenteritis may be attributable to pathogens in treated drinking water. However the results rely heavily on medication sales data from the single pharmacy that recorded over the counter medication sales. The authors note that increasing computerisation of sales records will expand the available dataset for future studies. They also comment on recent recognition of the need for better operational practices for water treatment which would be expected to reduce risks - eg avoidance of chlorination failures and control of individual filter performance at treatment plants.

This review article examines the phenotypic and genotypic characteristics of Helicobacter pylori, methods for in vitro culturing, evidence of its role in gastric pathogenicity, speculated modes of transmission and detection methods in food and water. H. pylori is associated with increased risks of chronic gastritis, peptic and duodenal ulcers, and adenocarcinoma and lyphoma of the stomach. It is estimated that about 10% of adults in developed nations harbour this bacterium, but occurrence rates are as high as 70 to 90% in developing countries.

The pathogen appears to be transmitted by the faecal-oral route but the importance of different modes of transmission (water, food, person to person etc) is uncertain. It has been difficult to isolate H. pylori from samples other than gastric tissues. H. pylori has the ability to survive in a viable but non-culturable coccoid (VNC) form which can not be cultured by traditional methods. Temperature has been found to be the main environmental factor associated with the development of VNC forms. VNC forms were found in water samples incubated at 4 and 15°C, but higher incubation temperatures (22 and 37°C) resulted in a loss of complete metabolic activity.

H. pylori is still viable and virulent in the VNC form, and can be detected by a number of methods including immunoseparation, molecular probes, autoradiography and ATP bio-luminescence. The authors suggest that such methods should be used to assess the prevalence of the organism in water, food and environmental samples.

This paper decribes an investigation of increasing reports of legionnaires’ disease in hospitals in San Antonio, Texas. The sixteen largest acute-care hospitals in the cities of San Antonio, Austin and Temple were selected for the study. Data was collected from all known legionnaires’ cases between January 1994 and January 1997, and microbiology laboratory databases of each hospital were reviewed for positive Legionella test results for the same period. From each hospital, water samples were collected from the bottom of all hot-water storage tanks and all water-heating tanks that supplied patient areas, or from hot-water return lines if tanks were not present. Water and swab samples were taken from shower heads and faucet aerators in patients rooms that were furthest from the hot-water source. Information was also collected on hospital infection control measures, microbiology testing practices and water system maintenance .

A total of twelve cases of nosocomial (acquired in hospital) legionnaires’ disease were found with eight of these occurring in 1996. A rise in cases occurred shortly after physicians started requesting Legionella urinary antigen tests. In San Antonio, Legionella was isolated from the water systems in 11 out of 12 hospitals. Cases of nosocomial legionellosis occurred in 5 hospitals. Those hospitals located in municipalities where water was treated with monochloramine as a residual disinfectant and those hospitals that had implemented control measures were Legionella-free. The 11 other hospitals had hot-water systems that were colonized with Legionella and were all supplied with drinking water that contained free chlorine as a residual disinfectant. Also in these infected hospitals the proportion of sites testing positive was inversely correlated with free residual chlorine concentration. Hot-water temperatures were too low in all hospitals to inhibit Legionella growth. The proportion of water-system sites testing positive for Legionella was a better predictor for risk of legionnaires’ disease in hospital patients than was the concentration of Legionella bacteria.

Comment The observations in this study support those in a previous paper by the same first author (see Health Stream Issue 13, p17). Chloramine persists longer than chlorine in distribution systems, and may also penetrate biofilms within pipes more readily. In discussing the risks of nosocomial infections, the authors note that the presence of highly susceptible patients (especially transplant patients) is a major risk factor. Most hospitals maintain hot water temperatures below 110 degrees F but raising water temperature slightly (to 122 degrees F) can substantially reduce Legionella colonisation with minimal risk of scalding to patients.

This paper describes a retrospective review of parasitology test data in the region of Lyon, France from May 1993 to December 1996. A single reference laboratory receives faecal specimens from a population base of 1.5 million. Findings were linked with survey data for HIV infection collected by the French Ministry of Health. HIV-infected persons had data collected on age, gender, risk factors for HIV, weight, CD4 cell count and the presence of diarrhea at the time of stool analysis. Other people who submitted stool specimens had data available that included age, gender and confirmation of serologic status regarding HIV infection. Drinking water in Lyon comes from the Rhone River and is chlorinated and distributed into three subsystems.

A total of 5692 stool samples from 1453 patients were assessed for microsporidia. Positive stools were found from 338 patients, including 261 (77%) HIV-infected patients, 16 (5%) transplant patients and 61 (18%) others with normal immune systems.. An increase in the percentage of stools positive for microsporidia was seen in May 1995 and was related to an increase in new diagnoses. This increase continued until November 1995, and during this period more than 50% of stools tested positive. A total of 200 cases occurred during the outbreak. There was no increase in cases of other protozoan pathogens (Cryptosporidium or Giardia). Analysis of risk factors for infection showed a strong statistical association with residence in one of the 3 water distribution systems. Routine water testing for faecal indicator organisms showed no noticeable problems with water quality.

The authors conclude that in HIV-infected persons the disease microsporidiosis appears to be endemic (prevalence about 0.1%) and the severity related to immunologic status. In people not infected with HIV the disease appears to be sporadic, with a prevalence of less than 1 in a million. Male homo/bisexuality was associated with microsporidiosis as was HIV infection, low CD4 cell counts and the presence diarrhea at time of analysis.

This study was undertaken to access the prevalence of non-tubercular mycobacteria in the swimming pool environment. Twelve public indoor swimming pools in the city of Bologna, Italy were examined. A chemical and microbiological examination was carried out on the water in each pool with 68 samples collected. Samples from each phase of treatment were taken including water leaving the pool, after filtration and after chlorination. Swabs were taken at four sites from each side of the pool edge, from the floor of each shower and from the changing-room benches, to measure microbiological contamination.

Non-tubercular mycobacteria were recovered from 88.2% of pool water samples with concentrations between 2 and 968 cfu/100ml. Most frequently isolated was Mycobacterium gordonae, being found in 73.5% of samples, next most frequent was M. chelonei isolated from 38.2% of samples, followed by M. fortuitum from 35.3% of samples.

Mycobacteria were found in 66.7% of samples of water entering the pool and 91.7% of samples of water leaving the pool. Mycobacteria were found in all samples from pool edges and shower floors but not from changing-room benches. M. gordonae was found in 80% of pool edge samples and 79.6% of shower floor samples. M. chelonei and M. fortuitum were also found frequently on pool edges and shower floors. Sporadic recoveries were made of M. flavescens, M. phlei and M. terrae from pool water, pool edge samples and shower floor samples. M.marinum was recovered on two occasions from shower floors.

Filtration and chlorination only brought about a slight reduction in the mycobacteria count. Results showed that the swimming pools provided a suitable habitat for the survival and reproduction of mycobacteria and that their presence was enhanced by high average pool temperatures and concentrations of chlorine that were lower than the 1mg/L free chlorine necessary to control mycobacteria. Mycobacterial disease has rarely been associated with swimming pool environments, with the exception of M.marinum skin infections (swimming pool granuloma). However, given the widespread presence of these microorganisms throughout the pool environment and the direct contact pool users have through water and resulting aerosols, the possible health risks for people with weakened immune systems should be considered.

In March 1998 an outbreak of gastroenteritis occurred in the Finnish municipality of Heinavesi. Heinavesi has a population of 4860 people and an area of 1318 km². About 2100 inhabitants live in the main village center which is supplied with municipal tap water from Lake Kermajarvi. Water treatment consists of sand filtration and chlorination. An increase in the number of patients with gastroenteritis attending the local health care centre was observed in March 1998 and in early April Norwalk-like virus (NLV) was found in patient’s stool samples.

A retrospective epidemiological study was initiated to discover the source of infection and determine the incidence of gastroenteritis. A questionnaire was given to every home in the municipality and included questions about recent symptoms of gastroenteritis, date and time of illness and illness among contact persons. Questions were also asked about eating history and consumption of municipal tap water. A total of 27 stool samples were examined from adults with acute gastroenteritis. Fifty three percent of the population answered the questionnaire.

It was estimated that between 1700-3100 cases of gastroenteritis occurred in the district in about 9 days, with all age groups equally represented. Symptoms were of short duration and only about 50 people sought medical attention. However about 800 working days were lost due to the illness, and total costs for the outbreak were estimated at US $300,000.

Those who used municipal water had a 3.5 times higher risk of developing disease than those who used water from a private well, boiled water or bottled water (95% CI, 3.11-3.96). NLV genogroup II (GGII) was identified by use of RT-PCR and amplicon sequencing in samples taken from untreated water, treated water and tap water and from fifteen of the 27 patient stool samples. From patients samples, both NLV GGI and GGII were detected. Some stool samples were also tested for bacterial pathogens and Cryptosporidium and Giardia, but none were positive. 89 people reported two episodes of illness, and secondary person to person transmission is likely to have been responsible for a substantial number of cases.

The source of the contamination of Lake Kermajarvi is uncertain, although it is possible that a large foodborne NLV outbreak in the city of Kuopio (70km upstream of Heinavesi) which occurred four months earlier, may have caused the outbreak. Another possible source was a service station with restaurant which discharged treated sewage about 6 km upstream of Heinavesi. At the time of the outbreak the water was covered with ice and low temperatures may have prolonged survival of the virus.

A review of water treatment records showed that during the outbreak chlorine concentrations were much lower (0.07 to 0.03 mg/L) than the goal value of 0.8 mg/L and not adequate to destroy NLVs. It is suggested that regular surveillance for viruses in drinking water should be considered in order to prevent waterborne viral epidemics.

In Palm Bay, Florida, the residents (approximately 40,000) rely on septic tanks for their sewage disposal and use wells as their primary source of drinking water. During July to September, the wet season, high levels of rain occur with mean precipitation greater than 63 cm. The result of these high levels of rain and the presence of porous sandy soils is high water tables and septic tank overflow. Septic tank leachate contaminates the groundwater as it can not percolate through the soil during the wet season and therefore poses a health risk to those drinking from local wells.

To determine the effects of season on fecal coliform and nutrient contamination of wells and to examine the effects of distance between wells and septic tanks, sixty residential wells in Palm Bay were tested for fecal coliforms, nitrates and phosphates. A well water questionnaire was distributed. Ground water samples were collected at various distances from septic tanks during the wet season and the dry season.

The results showed that samples collected during the wet season contained twice as many fecal coliforms and higher concentrations of nitrates and phosphates in comparison to samples collected during the dry season, with fecal coliform counts almost double in the wet season. A statistically significant correlation was found between increasing fecal coliform, nitrate and phosphates concentrations and decreasing distance between wells and septic tanks.

During 1997, 56 bottles of mineral waters were bought in randomly selected shops all over Europe and analysed for 66 elements. Median values for a number of elements were below detection: Ag, Er, Eu, Ga, Gd, Ho, In, PO₄, Pr, Sm, Sn, Tb, Tm, Yb. The highest median concentrations were found for Ca, SO₄, Na, Cl, Mg, K, Si, which were all above 1 mg/l.

Mineral waters with high total mineralisation came from Scandinavia, Russia and the Baltic States and Germany. Values of total mineralisation of water samples ranged from 19 to 6695 mg/l. Differences in concentration for single elements ranged from one to six orders of magnitude. Differences in composition were observed between regions due to geology of the area and to taste differences and local regulations. The type of bottle the water was sold in also influenced general water chemistry. It was found that waters stored in glass bottles had a much higher median Pb, U, Zr, Li, K and Na concentrations.

When results from the mineral waters tested were compared with currently valid action levels for drinking water, only 15 bottles out of 56 would pass all drinking water standards for inorganic constituents. For elements with known adverse health implications (As, Ba, Br, F, S and Ti) relatively few bottles exceeded action levels.

Such a large natural variation in concentration of elements seen in the mineral waters makes it apparent that little is known about the natural variation of elements in water. Action levels for drinking water are not necessarily set on a scientific or health related basis and the presumption is made that "natural" water is "clean" and does not show a large variation in element concentration. The results of this study suggest that it could be useful to analyse a wide range of elements and create a database on water chemistry for the whole of Europe. This could be used to create meaningful action levels for a small set of elements crucial for public health.

Comment The authors note that the EEC definition of "mineral water" relates to the protected nature of the source, with particular emphasis on bacteriological quality. This concept presupposes that "pollution" is the main threat to water quality, and does not consider that "natural" constituents of water may be harmful. Increasing numbers of people are using bottled waters of various types as their principal drinking water source, and may be exposed to hazardous levels of some elements. The paper also highlights the anomalies resulting from regulations which are not applied equally to products used for the same purpose.

This study examined the prevalence of enteric bacterial pathogens in the environment by analysing bacterial isolates from diarrhoeal patients, coastal waters and shellfish from Hong Kong Island. From January to December 1993, stool or rectal swabs were collected from patients with diarrhoea at Queen Mary Hospital. During 1992 and 1993, 24 water samples were collected from sites where there was known sewage pollution. During this time 12 shellfish samples (oysters, clams and mussels) were purchased from wet-markets at different localities.

A total of 1211 bacterial isolates from clinical samples were identified. Of these, Salmonellae were the most frequently identified (66%), followed by Campylobacter spp (13%) and Shigella spp (6%). From coastal waters 344 bacterial isolates were identified, of these 62% were Vibros, 18% were Salmonellae and 18% were Aeromonas. Of the 114 shellfish isolates, 89% were Vibros and 10% were Salmonellae.

Serotyping of the 870 Salmonella isolates showed that those occurring in water were different to those in hospital patients. Vibro species isolated from environmental samples did not include V. cholerae 01 nor V. cholerae 0139. It was concluded that bacterial pathogens present in coastal waters and shellfish in Hong Kong were not similar to those in hospital patients with severe gastroenteritis.

Aluminium Arsenic Cancer Disinfection Byproducts Gastroenteritis Helicobacter Legionella Microsporidia Mycobacteria Norwalk-like-virus Water Quality List of Articles	Disclaimer Whilst every effort is made to reliably report the data and comments from the journal articles reviewed, no responsibility is taken for the accuracy of articles appearing in Health Stream, and readers are advised to refer to the original papers for full details of the research.

From the Literature - Health Stream Issue 17 - March 2000