One of the mainstays of modern public health is the disinfection of water. While there are still communities drawing water from essentially sterile deep wells, most use surface water that must cleaned and disinfected before drinking. Chlorination is the most widespread and best understood technique for disinfecting water, and it is has an additional benefit that a small amount of the chlorine stays dissolved in the water (chlorine residual) and prevents the growth of infectious agents as the water is piped through non-sterile pipes into homes and businesses. While there are alternatives for chlorination, they do not have the proven safety record of chlorination and they would be expensive for many drinking water providers to adopt. This case involves an attempt by the Environmental Protection Agency (EPA) to ban chloroform from drinking water.
Chloroform is known to medical science as an anesthetic agent (though not one in general use anymore) and as a possible human carcinogen. Most chloroform in drinking water is formed when chlorine reacts with organic chemicals dissolved in the water, which results in a mix of chlorinated hydrocarbons. These occur in very small amounts but are present in most chlorinated water. Risk-benefit analysis indicates that it is safer to drink chlorinated water, with its tiny risk of carcinogenesis, than to not chlorinate or to use other agents, because the risk of serious or fatal water-borne illness is so much more serious than the risk carcinogenesis. The EPA, however, rejects the risk-benefit analysis approach and focuses only on the risk of chloroform toxicity and ignores the overall benefit chlorination. The EPA based its approach on the statutory guidance in the clean water act:
"The Safe Drinking Water Act ('SDWA' or the 'Act') directs the Environmental Protection Agency to set standards for the regulation of covered drinking water contaminants. For each EPA sets a 'maximum contaminant level goal' ('MCLG'), defined as 'the level at which no known or anticipated adverse effects on the health of persons occur and which allows an adequate margin of safety.' 42 U.S.C. § 300g-1(b)(4)(A). The MCLG is somewhat aspirational. After having set it, EPA is to promulgate an enforceable standard, known as a maximum contaminant level ('MCL'), which takes practical considerations into account while remaining 'as close to the [MCLG] as is feasible."
Based on this law, EPA originally set a MGLC of zero for chloroform. Congress then modified the Act and the EPA set up an expert study panel to review its standard for chloroform. The panel rejected the EPA's use of a linear method of estimating low level risk (such a method results in a finding of risk at all concentration levels) and found that there were safe levels for chloroform. Based on this analysis, the EPA set a MGLC of 300 parts per billion in its proposed rule. However, after the comment period, the EPA proposed a final rule of zero ppb for chlorine, explaining that this was within its statutory authority to choose a margin of safety. The plaintiff sued to force the EPA to follow the recommendations of its scientific advisors. The EPA countered that the MGLC did not matter because it uses the MCL for total trihalomethanes (of which chloroform is only one) as its enforcement threshold, and this MCL is set high enough to not threaten the use of chlorination. The EPA also made procedural objections to try to get the court to dismiss plaintiff's claims.
The court rejected the EPA's claim that only the MCL for total trihalomethanes mattered on evidence that its practice was to set lower allowable limits for chloroform than the limit for total trihalomethanes. More importantly, the court rejected the EPA's claim that its standard was only an interim regulation while it waited for better scientific studies. The court found that the statute said the regulatory decisions for establishing MGLCs and MCLs required the agency to use the best "available" science, not the best that might be available at some time in the future. The court rejected the claim that interim standards were not subject to this requirement, holding that such an exception would undermine congressional intent.
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