Drinking water, maximum concentration level

The USEPA has established maximum contaminant levels (MCLs) for public water supplies to reduce the chance of adverse health effects from contaminated drinking water. Maximum contaminant levels are enforceable limits that public water supplies must meet and are lower than concentrations at which health effects have been observed. The only PAH with an established MCL is benz(a) pyrene, which is regulated at 0.2 parts per billion. 

REGULATORY STATUS Criterion to protect freshwater aquatic life 0.0038 pg/L/24 hr avg., concentration not to exceed 0.52 pg/L Criterion to protect saltwater aquatic life 0.0036 pg/L/24 hr avg., concentration not to exceed 0.053 pg/L Criterion to protect human health preferably 0 lifetime cancer risk of 1 in 100,000 2.78 ng/L lifetime health advisory 0.4 pg/L Mexico limits in drinking water 0.018 mg/L drinking water maximum contaminant levels 0.2 pg/L Illinois standard 0.1 pg/L the following are guidelines in drinking water set by some states 0.1 pg/L (California), 0.006 pg/L (Kansas and Minnesota)... 

A second excellent, but limited, source of information is the list in the National Interim Primary Drinking Water Regulations its MCL (Maximum Concentration Level) values (8) are directly convertible to D-j values (1,2,3) by applying the factor weight of water consumed body weight ... 

In 1966 and 1967, when the use of endrin was not restricted, endrin was detected in 5 of 67 raw water samples from the Mississippi and Missouri Rivers (Schafer et al. 1969). At a later time when endrin use was substantially restricted, an Iowa study of 33 community water supplies using surface water found no detectable concentrations of endrin in the distribution systems (Wnuk et al. 1987). In an extensive water quality monitoring program conducted by the California Department of Health Services, endrin was detected (detection limit not specified) in only 2 of 5,109 public drinking water sources sampled from 1984 to 1992, at mean and maximum concentrations of 0.06 and 0.10 ppb, respectively (Storm 1994). Concentrations did not exceed the Maximum Concentration Level (MCL) of 0.2 ppb. In another recent study, endrin was not detected (detection limit not specified) in 32 samples each of raw water and highly treated reclaimed waste water undergoing evaluation as a possible supplement to raw water sources in San Diego, California (De Peyster et al. 1993). 

Maximum concentration level in drinking water (2,3,7,8-TCDD) 5 g/L... 

EPA has not established standards for all of the 260 chemicals. There are no maximum concentration level (MCL) standards for 141 of the 260 chemicals found in U.S. drinking water. The unregulated water contaminants are listed in Table 8.7J641... 

There are very few regulations and laws dealing with the presence of PCBs in water either at an international or national level. In these few cases the total PCB concentration is always indicated, but no mention is made about specific congeners. In particular, the U.S. Environmental Protection Agency (EPA) has fixed the maximum concentration level of PCBs in drinking water at... 

Pesticides are considered to be dangerous environmental pollutants. The US Environmental Protection Agency and European Union have established the maximum aUowed concentration of pesticides in drinking water at the level of 0.1 Xg/L for an individual pesticide and 0.5 Xg/L for the sum of pesticides, including their main metabohtes. It is clear, if the concentration of pesticides exceeds the above limit, water intended for human consumption has to be purified. Hypercrosshnked sorbents offer such an opportunity. 

The radiological hazard of tritium to operating personnel and the general population is controlled by limiting the rates of exposure and release of material. Maximum permissible concentrations (MPC) of radionucHdes were specified in 1959 by the International Commission on Radiological Protection (79). For purposes of control all tritium is assumed to be tritiated water, the most readily assimilated form. The MPC of tritium ia breathing air (continuous exposure for 40 h/wk) is specified as 185 kBq/mL (5 p.Ci/mL) and the MPC for tritium in drinking water is set at 3.7 GBq/mL (0.1 Ci/mL) (79). The maximum permitted body burden is 37 MBq (one millicurie). Whenever bioassay indicates this value has been exceeded, the individual is withdrawn from further work with tritium until the level of tritium is reduced. 

The use of chlorine dioxide in water systems results in its reduction to chlorite and chloride. In the UK the Drinking Water Inspectorate (DWI) restricts the use of chlorine dioxide in potable water supplies to a maximum of 0.5ppm total oxidants expressed as chlorine dioxide. This ensures that chlorite (and any chlorate) concentrations do not reach levels of potential harm to humans. 

There is uncertainty as to what levels of MTBE in drinking water cause a risk to public health.9 U.S. EPA has issued an advisory suggesting that drinking water should not contain MTBE in concentrations >20-40 pg/L, based on taste and odor concerns, but has not issued a federal maximum contaminant level (MCL) for MTBE, which will be based on the ongoing U.S. EPA studies.1... 

Fig. 32.2. Remediation of the aquifer shown in Figure 32.1, as the simulation continues. After water contaminated with Pb++ displaces half of the aquifer s pore volume, clean water is flushed through the aquifer until a total of 30 pore volumes have been replaced. Flushing attenuates Pb++ concentration in the groundwater (top), so that it gradually approaches drinking water standards (MCL, or Maximum Contamination Level), and slowly displaces most of the sorbed metal from the Fe(OH)3 surface, primarily from the weak surface sites.

Data for humans show that adverse effects occur at concentrations in air >1.0 mg PCP/m3 and in tissues at more than 8 mg/kg fresh weight (Table 23.7). No adverse effects were noted at daily intakes of 2.1 mg per 70-kg adult or 30 pg/kg BW, up to 1.01 mg/L in drinking water, <0.5 mg/m3 in air, <0.5 mg/L in blood plasma, and <1.0 mg/L in blood (Table 23.7). It is noteworthy that the recommended PCP air concentration of 0.5 mg/m3 results in a daily intake of 2.5 to 3.8 mg (based on 15 to 23 m3 of air inhaled daily, 8-h exposure), equivalent to 42 to 63 pg/kg BW for a 60-kg female. These levels are higher than the currently recommended no-adverse-effect level of 30 pg/kg BW daily (Table 23.7), and overlap or exceed the 58 to 74 pg/kg BW daily range — a level recommended by Williams (1982). Air concentrations >1.0 mg PCP/m3 can produce respiratory irritation in unacclimatized individuals, but concentrations as high as 2.4 mg/m3 can be tolerated by conditioned individuals (USEPA 1980). The biological tolerance value of <1000 pg PCP/L in blood, recommended by Ziemsen etal. (1987), is based on occupational air exposure studies exposure to maximum average air concentrations of 0.18 mg PCP/m3 for up to 34 years produced blood PCP residues of 23 to 775 pg/L, with no measurable adverse effects. The authors concluded... 

For maximum protection of human health from the potential carcinogenic effects of exposure to arsenic through drinking water or contaminated aquatic organisms, the ambient water concentration should be zero, based on the nonthreshold assumption for arsenic. But a zero level may not be attainable. Accordingly, the levels established are those that are estimated to increase cancer risk over a lifetime to only one additional case per 100,000 population. These values are estimated at 0.022 pg As/L for drinking water and 0.175 pg As/L for water containing edible aquatic resources (USEPA 1980 Table 28.7). 

Most water systems are required to monitor for radioactivity and certain radionuclides, and to meet maximum contaminant levels (MCLs) for these contaminants, to comply with the Safe Drinking Water Act (SDWA). Currently, USEPA requires drinking water to meet MCLs for beta/photon emitters (includes gamma radiation), alpha particles, combined radium 226/228, and uranium. However, this monitoring is required only at entry points into the system. In addition, after the initial sampling requirements, only one sample is required every three to nine years, depending on the contaminant type and the initial concentrations. 

In a recent study in Australia, Thompson et al. [121] assessed the exposure to PFCs via potable water in Austraha. Sixty-two samples of potable water were collected from 34 locations across Austraha, including capital cities and regional centre. PFOS and PFOA were the most commonly detected compounds, and quantifiable levels were found in 49% and 44% of all samples, respectively. The maximum concentration in any sample was seen for PFOS with a concentration of 16 ng/L, second highest maximums were for PFHxS and PFOA at 13 and 9.7 ng/L. Assuming a daily intake of 1.4 and 0.8 ng/kg b.w. for PFOS and PFOA the average contribution from drinking water was 2-3% with a maximum of 22% and 24%, respectively. 

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