GUIDELINES FOR DRINKING-WATER QUALITY

Reason for not establishing Occurs in drinking-water at concentrations well below those of health a guideline value concern Assessment date 2003 Principal references FAO/WHO (2000) Pesticide residues in food—1999 evaluations WHO (2003) 2-Phenylphenol and its sodium salt in drinking-water

2-Phenylphenol has been determined to be of low toxicity. Both 2-phenylphenol and its sodium salt are carcinogenic in male rats, and 2-phenylphenol is carcinogenic in male mice. However, urinary bladder tumours observed in male rats and liver t­umours observed in male mice exposed to 2-phenylphenol appear to be threshold phenomena that are species and sex specific. JMPR concluded that 2-phenylphenol is unlikely to represent a carcinogenic risk to humans. Although a working group c­onvened by IARC classified 2-phenylphenol, sodium salt, in Group 2B (possibly carcinogenic to humans) and 2-phenylphenol in Group 3 (not classifiable as to its carcinogenicity to humans), JMPR noted that the IARC classification is based on hazard identification, not risk assessment, and is furthermore limited to published literature, excluding unpublished studies on toxicity and carcinogenicity. JMPR also concluded that there are unresolved questions about the genotoxic potential of 2-phenylphenol. A health-based value of 1 mg/l can be calculated for 2-phenylphenol on the basis of an ADI of 0–0.4 mg/kg body weight, based on a NOAEL of 39 mg/kg body weight per day in a 2-year toxicity study on the basis of decreased body weight gain and hyperplasia of the urinary bladder and carcinogenicity of the urinary bladder in male rats, using an uncertainty factor of 100 for interspecies and intraspecies variation. Because of its low toxicity, however, the health-based value derived for 2-phenyl- phenol is much higher than concentrations of 2-phenylphenol likely to be found in drinking-water. Under usual conditions, therefore, the presence of 2-phenylphenol in drinking-water is unlikely to represent a hazard to human health. For this reason, the establishment of a formal guideline value for 2-phenylphenol is not deemed ne- cessary.

Polynuclear aromatic hydrocarbons Polynuclear aromatic hydrocarbons, or PAHs, form a class of diverse organic com- pounds each containing two or more fused aromatic rings of carbon and hydro- gen atoms. Most PAHs enter the environment via the atmosphere from a variety of combustion processes and pyrolysis sources. Owing to their low solubility and high affinity for particulate matter, they are not usually found in water in notable ­concentrations. The main source of PAH contamination in drinking-water is usu- ally the coal tar coating of drinking-water distribution pipes, used to protect the pipes from corrosion. Fluoranthene is the most commonly detected PAH in drink- ing-water and is associated primarily with coal tar linings of cast iron or ductile iron distribution pipes. PAHs have been detected in a variety of foods as a result of the deposition of airborne PAHs and in fish from contaminated waters. PAHs are also formed during some methods of food preparation, such as char-broiling, grilling,

410 12. CHEMICAL FACT SHEETS roasting, frying or baking. For the general population, the major routes of exposure to PAHs are from food and ambient and indoor air. The use of open fires for heat- ing and ­cooking, which is common especially in developing countries, may increase PAH exposure. Where there are elevated levels of contamination by coal tar coatings of water pipes, PAH intake from drinking-water could equal or even exceed that from food.

Guideline value Benzo[a]pyrene: 0.0007 mg/l (0.7 µg/l) Occurrence PAH levels in uncontaminated groundwater usually in range 0–5 ng/l; concentrations in contaminated groundwater may exceed 10 µg/l; typical concentration range for sum of selected PAHs in drinking-water is from about 1 ng/l to 11 µg/l Basis of guideline value Based on an oral carcinogenicity study in mice and calculated using a derivation two-stage birth–death mutation model, which incorporates variable dosing patterns and time of killing; quantification of dose–response for tumours, on the basis of new studies in which the carcinogenicity of benzo[a]pyrene was examined following oral administration in mice, but for which the number of dose groups was smaller, confirms this value Limit of detection 0.01 µg/l by GC-MS and reversed-phase HPLC with a fluorescence ­detector Treatment performance 0.05 µg/l should be achievable using coagulation Additional comments The presence of significant concentrations of benzo[a]pyrene in drinking- water in the absence of very high concentrations of fluoranthene indicates the presence of coal tar particles, which may arise from seriously deterior- ating coal tar pipe linings. It is recommended that the use of coal tar–based and similar materials for pipe linings and coatings on storage tanks be discontinued. Assessment date 1998 Principal reference WHO (2003) Polynuclear aromatic hydrocarbons in drinking-water

Reason for not establishing Fluoranthene: Occurs in drinking-water at concentrations well below a guideline value those of health concern Assessment date 1998 Principal reference WHO (2003) Polynuclear aromatic hydrocarbons in drinking-water

Evidence that mixtures of PAHs are carcinogenic to humans comes primarily from occupational studies of workers following inhalation and dermal exposure. No data are available for humans for the oral route of exposure. There are few data on the oral t­oxicity of PAHs other than benzo[a]pyrene, particularly in drinking- water. Relative potencies of carcinogenic PAHs have been determined by compari- son of data from dermal and other studies. The order of potencies is consistent, and this scheme therefore­ provides a useful indicator of PAH potency relative to that of benzo[a]pyrene.

411 GUIDELINES FOR DRINKING-WATER QUALITY

A health-based value of 4 µg/l can be calculated for fluoranthene on the basis of a NOAEL of 125 mg/kg body weight per day for increased serum glutamate–pyruvate­ transaminase levels, kidney and liver pathology, and clinical and haematological changes in a 13-week oral gavage study in mice, using an uncertainty factor of 10 000 (100 for interspecies and intraspecies variation, 10 for the use of a subchronic study and inadequate database and 10 because of clear evidence of co-carcinogenicity with benzo[a]pyrene in mouse skin painting studies). However, this health-based value is significantly above the concentrations normally found in drinking-water. Under usual conditions, therefore, the presence of fluoranthene in drinking-water does not repre- sent a hazard to human health. For this reason, the establishment of a formal guideline value for fluoranthene is not deemed necessary.

Potassium Potassium is an essential element in humans and is seldom, if ever, found in drinking- water at levels that could be a concern for healthy humans. The recommended daily requirement is greater than 3000 mg. Potassium occurs widely in the environment, including all natural waters. It can also occur in drinking-water as a consequence of the use of potassium permanganate as an oxidant in water treatment. In some coun- tries, potassium chloride is being used in ion exchange for household water softening in place of, or mixed with, sodium chloride, so potassium ions would exchange with calcium and magnesium ions. Possible replacement or partial replacement of sodium salts with potassium salts for conditioning desalinated water has been suggested. The latter seems to be an unlikely development at this stage, in view of the cost difference.

Reason for not establishing Occurs in drinking-water at concentrations well below those of health a guideline value concern Assessment date 2009 Principal reference WHO (2009) Potassium in drinking-water

Currently, there is no evidence that potassium levels in municipally treated drink- ing-water, even water treated with potassium permanganate, are likely to pose any risk for the health of consumers. It is not considered necessary to establish a health-based guideline value for potassium in drinking-water. Although potassium may cause some health effects in susceptible individ- uals, potassium intake from drinking-water is well below the level at which adverse health effects may occur. Health concerns would be related to the consumption of ­drinking-water treated by potassium-based water treatment (principally potassium chloride for regeneration of ion exchange water softeners), affecting only individuals in high-risk groups (i.e. individuals with kidney dysfunction or other diseases, such as heart d­isease, coronary artery disease, hypertension, diabetes, adrenal insufficiency, pre-existing hyperkalaemia; people taking medications that interfere with normal potassium-dependent functions in the body; and older individuals or infants). It is recommended that susceptible individuals seek medical advice to determine wheth- er they should avoid the consumption of water (for drinking or cooking) treated by w­ater softeners using potassium chloride.

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