The initial Safe Drinking Water Act (SDWA) was signed into law on December 16, 1974, (PL 93-253). This paper will summarize the evolution of both the SDWA and the resultant regulations, and focus on three new shifts in the national regulatory development process:
- Regulating contaminants as a group rather than one at a time;
- Improved analytical methods which can drive down standards; and
- New health effects data and its potential impact on drinking water standards.
All three have the potential to significantly impact the national regulatory development process and ultimately, potentially impact water utilities and their customers.
The 1974 SDWA established the basic national drinking water regulatory framework by which the US Environmental Protection Agency (USEPA), state and local regulatory agencies, and water utilities continue to provide safe drinking water. The 1974 SDWA shifted from allowing the states to set their own standards based on US Public Health Service guidelines to USEPA developing national enforceable standards. Primacy for the state regulatory programs, i.e., the states’ legal authority to continue their own regulatory programs, is contingent on the states’ standards being at least as strict as the federal standards and the states having the appropriate enforcement authority. Currently, 49 states and one tribe have primacy and oversee the public water systems, with some federal assistance and oversight.
The 1974 SDWA established a two-step process for developing national drinking water standards that is still used by USEPA. The agency sets a Maximum Contaminant Level Goal (MCLG), which is a non-enforceable health-based goal. The MCLG is the maximum level of a contaminant at which no known or anticipated adverse health effects would occur, allowing for an adequate margin of safety. USEPA has a policy of setting the MCLG at zero for carcinogens. Then, USEPA sets the enforceable, numerical Maximum Contaminant Level (MCL) as close as feasible to the MCLG, taking into account the best available technology, treatment techniques, and analytical methods, and cost considerations.
Drinking water standards have been moving from mg/L to µg/L, and new instrumentation can now routinely and reliably go down in the ηg/L range
The SDWA was amended in 1986 and 1996 (PL 99-339 and PL 104-208). From 1975-2006, USEPA finalized 18 major drinking water regulations, with an equal split between pre-1996 and post-1996 SDWA. Currently, 91 contaminants are regulated under these 18 national regulations.
The Current State of the Regulations
USEPA has regulated a handful of new contaminants since the 1996 SDWA (radionuclides, Disinfection By-Products [DBPs], and disinfectants). The nine post-1996 regulations that were finalized by USEPA were primarily regulations such as arsenic, that had specific regulatory deadlines in the 1996 SDWA. Five of these regulations were from the Microbial/Disinfection By-Product (M/DBP) Cluster of regulations, where paired regulations were developed to simultaneously tighten DBP and microbial standards.
The 1996 SDWA established a new, two-step process for identifying contaminants of concern for potential regulation. A Contaminant Candidate List (CCL) is developed on a five-year cycle, and then USEPA must make decisions whether to regulate, known as regulatory determinations, also on a five-year cycle. USEPA made two rounds of regulatory determinations for 20 new contaminants in 2003 and 2008 and determined that none of the contaminants provided a “meaningful opportunity for risk reduction” as mandated by the 1996 SDWA (USEPA, 2003, 2008). For example, in the first regulatory determination in 2003, USEPA decided that sodium (salt) should not be regulated in drinking water due the larger exposure from food. In the second regulatory determination in 2008, USEPA decided not to regulate five organic chemicals as, based on a national monitoring study, no occurrence was found in treated drinking water.
Regulating Contaminants as a Group
Even with the nine new regulations from 1998-2006, some in Congress and the Obama Administration perceive the lack of new regulations for new contaminants as a lack of progress, and have pressured USEPA to take action to develop new standards for new contaminants. In March 2010, USEPA released a new drinking water strategy with four components, with one of the components being to regulate contaminants as a group rather than one at a time (USEPA, 2010a). Regulating as a group has some precedent under the SDWA with Total Trihalomethanes (TTHMs) and five of the haloacetic acids (HAA5) being regulated under the M/DBP Cluster, and other groups such as gross alpha and beta photon/particle emitters, that are regulated under the Radionuclides Rule (USEPA, 1998, 2000, 2006).
"New health effects data for other health effects, such as neurotoxicity, reproductive, and developmental endpoints, is now available for many of these contaminants."
But making groups a major regulatory focus is something new, and utilities are concerned about making regulatory decisions that ultimately result in advanced treatment (with increased costs to consumers) based on limited health effects data. The SDWA requirement for the use of “…best available, peer-reviewed science…” should not be abandoned in the quest to simply increase the number of regulated contaminants. As treatment costs increase with advanced treatment, utilities need increased certainty in the health effects data to be able to justify increased rates to their customers. USEPA intends to announce its first group decision in early 2011.
Improved Analytical Methods
In addition to this political pressure, improved analytical methods are driving down drinking water standards. Drinking water standards have been moving from mg/L to µg/L, and new instrumentation can now routinely and reliably go down in the ηg/L range. These improved analytical methods have an impact on those drinking water standards with a MCLG of zero, as the current drinking water standard was set at the feasible level of the analytical method at the time. But how low can we go with drinking water standards? Again, utilities are concerned about regulators making decisions that ultimately result in advanced treatment (with increased costs to consumers) based on limited health effects data.
The 1996 SDWA also mandated that USEPA review existing drinking water regulations every six years, known as the six-year review. In its second six-year review, finalized in March 2010, USEPA reviewed 71 existing regulations and decided to revise four: trichloroethylene (TCE), tetrachloroethylene (PCE), acrylamide, and epichlorohydrin (USEPA, 2010b). TCE and PCE both have MCLGs of zero and MCLs of 5 µg/L, and USEPA decided that the standards could be revised due to analytical method improvements. In the Federal Register notice for the second six-year review, USEPA analyzed alternative standards of 2.5 µg/L, 1 µg/L, and 0.5 µg/L. The schedule for proposing, and ultimately finalizing, the revised TCE and PCE standards is unclear at this time.
TCE and PCE are just two of the currently regulated chemicals contaminants that are carcinogens with MCLGs of zero, and 21 other current standards for organic chemicals, one DBP, and the four radionuclides also have zero MCLGs. As analytical methods continue to improve, the potential for more drinking water standards to be lowered will increase in the third and fourth six-year reviews.
New Health Effects Data
The 84 standards for chemical contaminants and radionuclides were established in the ‘80s and ‘90s, and many of the standards were based on a person drinking 2 L/day of the same water for 70 years. Almost all of these standards are based on an annual average of quarterly samples or the value of a single annual sample if the system is on reduced monitoring. New health effects data for other health effects, such as neurotoxicity and/or reproductive/developmental endpoints, is now available for many of these contaminants. It is likely that some of the contaminants that were regulated as carcinogens may, at some point in the future, be revised under a six-year review and will be regulated based on other adverse health effects with a shorter timeframe. This would be a significant shift in drinking water regulations. Compliance could be based on a shorter timeframe, such as quarterly, monthly, weekly, or even a single sample.
"Drinking water standards have to be based on the “best available, peer-reviewed science” as mandated by the SDWA, and it is challenging for the regulatory development process to keep up with the science."
A significant increase in the availability, accuracy, and reliability of online monitoring would be necessary for drinking water compliance to be based on shorter timeframes so that utilities would be able to make the necessary adjustments, such as adjusting treatment, to remain in compliance. Sensor technologies for critical chemical and microbial analyses such as TTHM online samplers and viable bacterial monitors are prohibitively difficult to deploy in typical utility operational locations throughout the distribution system. USEPA proposed the Revised Total Coliform Rule in 2010, but that proposal still uses analytical methods developed in the late ‘80s (USEPA, 2010c).
The 1996 SDWA and the 1996 Food Quality Protection Act (FQPA) started the development of the USEPA’s Endocrine Disruptor Screening Program (EDSP). On November 17, 2010, USEPA released its second list of 134 chemicals to be screened under the EDSP (USEPA, 2010d). This list includes many current regulated chemicals and many on the Third CCL (CCL3). Two of the interesting policy issues yet to be addressed under the EDSP are:
- How to address naturally occurring contaminants; and
- How to address Disinfection By-Products (DBPs) since this class of chemicals is not manufactured in the traditional sense and disinfection is mandated under current drinking water regulations.
The screening and testing of these SDWA and CCL3 contaminants will likely take several years, and even more time will be needed to incorporate this new health effects data info future six-year reviews. But the listing of these SDWA and CCL3 chemicals under EDSP shows the potential for the regulation of these contaminants to be based on something different than drinking 2 L/day of water from the same source for 70 years.
Drinking water standards have to be based on the “best available, peer-reviewed science” as mandated by the SDWA, and it is challenging for the regulatory development process to keep up with the science. More investment is needed on fundamental health effects, analytical methods, and treatment research to select the appropriate contaminants to regulate, and once that selection has been made, to determine what level is “safe”. But keeping up with the science is the only way to assure the public that the drinking water will continue to be safe in the future as more health effects data becomes available, and as analytical methods continue to improve and as more contaminants are found in drinking water at lower and lower levels.
USEPA, 1998. Stage 1 Disinfectants and Disinfection By-Products Rule; Final Rule. Fed. Reg., 63:241:69389.
USEPA, 2000. Radionuclides; Final Rule. Fed. Reg., 65:236:76708.
USEPA, 2003. Announcement of Regulatory Determinations for Priority Contaminants on the Drinking Water Contaminant Candidate List; Notice. Fed. Reg., 68:138:42897.
USEPA, 2006. Stage 2 Disinfectants and Disinfection By-Products Rule; Final Rule. Fed. Reg., 71:2:387.
USEPA, 2008. Regulatory Determinations Regarding Contaminants on the Second Drinking Water Contaminant Candidate List; Notice. Fed. Reg., 73:147:44251.
USEPA, 2010a. Drinking Water Strategy. http://water.epa.gov/lawsregs/rulesregs/sdwa/dwstrategy/index.cfm (accessed January 19, 2011).
USEPA, 2010b. Announcement of the Results of EPA's Review of Existing Drinking Water Standards and Request for Public Comment and/or Information on Related Issues; Notice. Fed. Reg. 75:59:15499.
USEPA, 2010c. Revisions to the Total Coliform Rule; Proposed Rule. Fed. Reg., 75:134:40926.
USEPA, 2010d. Endocrine Disruptor Screening Program; Second List of Chemicals for Tier 1 Screening; Notice. Fed. Reg., 75:224:70248.