United States drinking water, lead

In a more recent Lederal Register notice (EPA 1991d), EPA examined the occurrences of lead in source water and distributed water. By resampling at the entry point to the distribution system, few samples were found to contain lead at levels above 5 pg/L. EPA now estimates that approximately 600 groundwater systems may have water leaving the treatment plant with lead levels above 5 pg/L. Based on several data sets, it is estimated that less than 1% of the public water systems in the United States have water entering the distribution system with lead levels above 5 pg/L. These systems are estimated to serve less than 3% of the population that receives drinking water from public systems (EPA 199 Id). 

The majority of 1,2-dichloroethane released into the environment enters the atmosphere from its production and use as a chemical intermediate, solvent and lead scavenger in gasoline. It has been detected at low levels in ambient and urban air, groundwater and drinking-water samples (United States National Library of Medicine, 1997). 

Three most commonly used fluoride chemicals in the United States for fluoridation are sodium fluoride, sodium silicofluoride, and hydrofluosilicic acid. When applied to drinking water, they should meet the AWWA Standard B703-00 and B701-99 and should be NSF/ANSI Standard 60 certified. These sfandards ensure quality of the chemicals and limit the amount of impurities in the chemical, such as heavy metals (lead) (3,14,15). 

In an effort to reduce lead emissions into the environment, MTBE has been introduced into petrol as an alternative in a number of countries. Since its introduction in the late 1980s it has become one of the top four chemicals in terms of mass production in the United States. Unfortunately, by the beginning of the twenty-first century many drinking water sources, in the United States in particular, had become contaminated with this chemical, which is of concern for both health and esthetic considerations [50]. 

Dioxins are released in the environment in emissions from the incineration of mimicipal refuse and certain chemical wastes and in exhaust from automobiles powered by leaded gasohne. Dioxins are highly persistent and accumulate in the environment. They are highly toxic and exhibit endocrine-disrupting activity. Therefore, they are regulated by authorities, e.g., in the United States for the most toxic 2,3,7,8-TCDD the maximum allowed concentration in drinking water is 10 ngmL [21]. 

Potable water should be supplied under continuous positive pressure in a plumbing system free from defects that could lead to the contamination of APIs or intermediates. Potable water should meet the standards prescribed in the Environmental Protection Agency s Primary Drinking Water Regulations (Title 40, Code of Federal Regulations, Part 141). Potable water in facilities outside the United States should meet comparable standards of the European Union, Japan, the World Health Organization, or other authorities. Drains should be of adequate size and provided with an air break or suitable mechanical device to prevent back-siphonage. 

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