I’ll be the first to admit that this topic is one that puts most people to sleep. But for the regulatory geeks among us, it can be an interesting process, full of nuance and surprise. OK, maybe that’s a bit much, but it’s definitely an important process that it’s good for everyone in the drinking water business to have some understanding of, so let’s dive in.
Drinking water regulations come primarily from two levels of government. Regulation at the Federal level come through the United States Environmental Protection Agency (US EPA or just EPA), and at the state level through the California Dept of Public Health. Since federal regulations generally trump state regulations, we'll start by going over the regulatory process for the US EPA, and save the - the potential adverse effects of the contaminant on the health of humans,
- the frequency and level of contaminant occurrence in public drinking water systems, and
- whether regulation of the contaminant presents a meaningful opportunity for reducing public health risks 4
The Third Contaminant Candidate List was finalized by the EPA on October 9, 2009 . It contains 104 chemicals or chemical groups, and 12 microbiological contaminants. The EPA started with 7,500 potential contaminants selected from pesticides, disinfection byproducts, chemicals used in commerce, waterborne pathogens, pharmaceuticals, biological toxins, and other sources. Contaminants were chosen based on expert evaluations of the potential for the contaminant to occur in public water systems and the potential for public health concern. The EPA is currently working on CCL 4, which is scheduled to be proposed early this year.
As I mentioned, choosing to make a regulatory determination on a contaminant listed on the CCL requires that the EPA evaluate these three criteria:
- Will the contaminant have an adverse effect on the health of humans? This includes determining what the adverse effect is (cancer, liver damage, thyroid problems) and the level of exposure at which the adverse effect occurs, known as the level of concern.
- Does the contaminant occur in public water supplies at the level of concern, and if so, how frequently? This information is collected from sampling data, including research data from the United States Geologic Survey; United States Dept of Agriculture pesticide data program; chemical production data; and from the data collected by the Unregulated Contaminant Monitoring Rule, or UCMR.
- Is there a meaningful opportunity for health risk reduction? A number of factors are taken into consideration for this, including the number of people who are at risk of exposure from drinking water; whether the contaminant has particular effects on sensitive populations such as children, the elderly, or those with compromised immune systems; and the relative exposure from water versus other sources such as food.
After the EPA makes a regulatory decision on a contaminant, the next step is to set a Maximum Contaminant Level Goal (MCLG). The EPA reviews numerous health effects studies before setting the MCLG, the maximum level of a contaminant in drinking water at which no known or anticipated adverse effect on the health of persons would occur, and which allows an adequate margin of safety. MCLGs are non-enforceable public health goals. Since MCLGs consider only public health and not the limits of detection and treatment technology, sometimes they are set at a level which water systems cannot meet. When determining an MCLG, EPA considers the risk to sensitive subpopulations (infants, children, the elderly, and those with compromised immune systems) of experiencing a variety of adverse health effects. For microbial contaminants that may present public health risk, the MCLG is set at zero because ingesting one protozoa, virus, or bacterium may cause adverse health effects. If there is evidence that a chemical is a carcinogen, a substance which may cause cancer, and there is no dose below which the chemical is considered safe, the MCLG is set at zero. If a chemical is carcinogenic and a safe dose can be determined, the MCLG is set at a level above zero that is safe. For chemicals that can cause adverse non-cancer health effects, the MCLG is based on the reference dose. A reference dose (RfD) is an estimate of the amount of a chemical that a person can be exposed to on a daily basis that is not anticipated to cause adverse health effects over a person's lifetime. In RfD calculations, sensitive subgroups are included, and uncertainty may span a factor of 10 or more. The RFD is multiplied by body weight and divided by daily water consumption to provide a Drinking Water Equivalent Level (DWEL). The DWEL is multiplied by the relative source contribution which is the percentage of the RfD remaining after considering other exposure routes (e.g. food, inhalation, etc.) to determine the MCLG.
Once the MCLG is determined, EPA sets an enforceable standard. In most cases, the standard is a Maximum Contaminant Level (MCL ), the maximum permissible level of a contaminant in water which is delivered to any user of a public water system. When there is no reliable method that is economically and technically feasible to measure a contaminant at particularly low concentrations, a Treatment Technique (TT) is set rather than an MCL . A treatment technique is an enforceable procedure or level of technological performance, which public water systems must follow to ensure control of a contaminant. The MCL is set as close to the MCLG as feasible. EPA must determine the feasible MCL or TT which the Safe Drinking Water Act defines as the level that may be achieved with the use of the best available technology, treatment techniques, and other means which EPA finds are available (after examination for efficiency under field conditions, not solely under laboratory conditions) are available, taking cost into consideration. EPA must also prepare a Health Risk Reduction and Cost Analysis (HRRCA) in support of any new MCL that analyzes all benefits that are likely to occur as the result of compliance with the proposed standard. They must also analyze any increased costs that will result from the proposed drinking water standard. EPA must also consider costs and benefits associated with a range of MCL values; health effects to the general population and sensitive sub-populations; and any increased health risk to the general population that may occur as a result of the new MCL . Primary drinking water standards go into effect three years after they are finalized. If capital improvements are required, EPA's Administrator or a state may allow this period to be extended up to two additional years.
Wow – that’s a lot to go through to implement a new regulation. No wonder it can take so long for this process to work itself out. Next time we’ll look at the process of setting regulations specific to the State of California .
