By Lynda Huckestein, Project Chemist, Kelso, WA
Aquatic Humic Substances (AHS) result from the decomposition of plant and animal residues and are found in soil, sediment, and water. They are widespread in nature and are mostly comprised from naturally occurring dissolved organic matter in water.
EPA is developing a new approach to managing drinking water and is currently seeking comments by the public and stakeholders, including utilities, rural communities, and states.
The new approach will focus on four areas:
By Chris Leaf, Project Chemist, Kelso, WA
Imagine turning on a faucet to get a glass of water and discovering that perfluorooctane sulfonic acid, methyl tert-butyl ether, or chloromethane has flowed into your glass. These chemical compounds represent real threats to the public and are present in many public water supplies today.
In September of 2009, the EPA finalized its Contaminant Candidate List 3 (CCL3), comprised of 116 drinking water contaminants. These contaminants have already been discovered in public water systems or pose the risk of existing in public water supplies. Under the Safe Drinking Water Act (SDWA), the EPA is required to evaluate and determine whether to regulate at least five contaminants from the CCL every five years. The EPA decides if regulations will be required based on the following criteria1:
A recent United States Geological Survey (USGS) study of public drinking water wells in California, Connecticut, Nebraska and Florida found that some were contaminated, but in amounts so minimal, human health was unlikely to be affected. The USGS tracked the movement of contaminants in groundwater and public-supply wells in four different aquifers.
According to the USGS, wells are not equally vulnerable to contamination because of differences in three factors: the general chemistry of the aquifer, groundwater age, and direct paths within aquifer systems that allow water and contaminants to reach a well. The importance of each factor differs among the various aquifer settings, depending upon natural geology and local aquifer conditions, as well as human activities related to land use and well construction and operation. However, the USGS feels that the study of the four different aquifer systems can be applied to similar aquifers and wells throughout the nation.
This article describes the background, stages and the new deadlines for public water systems to comply with the most current disinfectants and disinfection byproducts rule.
By Dr. Harlan H. Bengtson, PE
Background on Disinfection and Disinfection Byproducts
Jersey City, NJ was the first U.S. city to routinely disinfect its municipal water supply, starting in 1908.1 Soon after, thousands of cities and towns across the country began to do the same and this dramatically decreased the prevalence of waterborne diseases such as cholera and typhoid. To demonstrate, the incidence rate of typhoid fever in the U.S. dropped from about 100 cases per 100,000 people in 1900 to 33.8 cases per 100,000 people in 1920.2 By 2006, this rate had dropped to 0.1 cases per 100,000 people.3
Every day millions of gallons of treated and untreated wastewater are discharged into the waterways of the world. This wastewater may contain varying concentrations of pharmaceuticals and personal care products (PPCPs) including prescription and over the counter medications, nutraceuticals, illicit drugs, detergents, perfumes, insect repellent, sunscreens, and steroids, some of which have been identified in a recent article by The Associated Press1.
Recent studies have shown that many of these PPCP compounds at low concentrations can have negative effects on the endocrine systems of aquatic organisms. These compounds are collectively known as Endocrine Disrupting Compounds (EDCs). Other concerns regarding PPCPs include contamination of drinking water, estrogenic effects on humans and wildlife, and development of antibiotic resistant bacteria.
In 1999 and 2000, a study was performed by the USGS (Koplin, et al, 20002) in which the concentrations of 95 of these compounds were measured in 139 streams in 30 states (mostly downstream from intense urbanization and livestock production). Eighty-two of the 95 compounds of interest were found and 80% of the streams tested contained one or more of these compounds. Multiple compounds were found in many samples. The average number was seven and the greatest number was 38. Concentrations were low, rarely exceeding health advisories or aquatic-life criteria. However, advisory limits are not available for many of these compounds. Little is known about the effects of long-term low exposure to these compounds, potential interactions with other compounds in the environment (synergistic or antagonistic), possible cumulative effects over time, or what effect any degradation products of these compounds may have.
These compounds enter the environment from a wide variety of sources including agriculture use of pesticides and antibiotics, industrial discharges, and household use of chemicals and pharmaceuticals. Most wastewater treatment and domestic septic systems are not designed to remove these compounds. In another USGS study (Stackelberg et al., 20043), between 11 and 17 of these compounds were found in all finished drinking water samples at a conventional water treatment plant.
Analytical testing for these compounds requires the use of sophisticated instrumentation and experienced chemists. Due to their chemical nature, many of these compounds are not amenable to standard environmental gas chromatographic (GC) techniques. They are generally larger, less volatile, and more polar than other organic compounds that can be analyzed via GC and GC/MS techniques. Some of these compounds are also thermally labile, breaking down at elevated GC temperatures. Since PPCPs include many different classes of compounds with varying physical and chemical properties, Liquid Chromatography/Mass Spectroscopy/Mass Spectroscopy (LC/MS/MS) provides a convenient approach for determining a relatively wide range of chemicals of interest.4
On Tuesday, January 11th, 2005 the Committee to Access the Health Implications of Perchlorate Ingestion, convened by the National Research Council at the request of the EPA, DOD, NASA, and the DOE, released their report on the adverse health effects of perchlorate ingestion from clinical, toxicological and public health perspectives. The report also evaluated relevant scientific literature and key fi ndings of the EPA’s 2002 draft risk assessment document on perchlorate. The full report can be found on-line at http:// www.nap.edu/catalog/11202.html.
The committee noted that a noobserved- effect level (NOEL) or lowestobserved- adverse-effect level (LOAEL) identifi ed from a critical study, is used as the basis for establishing a reference dose for daily oral exposures. The committee decided to use a NOEL rather than a LOAEL as the basis for perchlorate risk assessment. They based their reference daily dose on the identified critical study done by Greer, et al (2002)1 in which healthy men and women were given doses of perchlorate of 0.007 to 0.5 mg/Kg body weight per day for 14 days. In this study, the NOEL was found to be 0.007 mg/Kg/day. Using this amount and applying an uncertainty factor of 10 to protect the most sensitive population (identifi ed as pregnant women who may have hypothyroidism or iodide defi ciency), the committee recommended a reference daily dose of perchlorate of 0.0007 mg/Kg of body weight per day from all sources. The EPA’s draft reference daily dose from the 2002 risk assessment was 0.00003 mg/Kg per day. The committee also noted that additional studies are needed, especially long-term, chronic exposure as well as clinical, mechanistic and epidemiological studies.
The release of the report generated a flurry of media reports with widely different safe drinking water levels touted – everything from maximum levels of 3 ppb to 200 ppb. However, as of February 18, 2005, the EPA has set an offi cial reference dose (RfD) of 0.0007mg/kg/day of perchlorate consistant with the National Research Council’s reference dose. The EPA translates the new RfD to a Drinking Water Equivalent Level (DWEL) of 24.5 ppb. As new information becomes available, CAS will post updates at www.caslab.com.
Learn more about Perchlorate Testing…
1 Greer, M/A., G, Goodman, R.C. Pleus, and S.E. Greer. 2002. Health effects assessment for environmental perchlorate contamination: The dose response for inhibition of thyroidal radioiodide uptake in humans. Environ. Health Perspect. 110:927
