Lab Science News

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