The State of California Office of Environmental Health and Hazard Assessment (OEHHA) recently set a new Public Health Goal for Perchlorate at 1 ppb. To help clarify, a public health goal is not a regulatory limit but is designated as a contaminant level where “…adverse health effects are not expected to occur.” This limit can be determined using ion chromatography without MS detection (link to downloadable application note).
Toxicity of Perchlorate for Humans
The OEHHA has based this new level on the known toxicity of perchlorate and its affect on the inhibition of iodide uptake by the thyroid gland and disruption of thyroid hormone production. Recent toxicological studies (in the literature) provide new information on exposures to and possible effects of perchlorate on infants as particularly susceptible. By law, the California Health and Safety Code Section 116365.2 incorporates updated drinking water ingestion rates. This lowers the previous PHG from 6 ppb to 1 ppb.
The California Safe Drinking Water Act of 19961 requires OEHHA to develop PHGs based exclusively on public health considerations. In turn, the PHGs published by OEHHA are considered by the State Water Resources Control Board in setting drinking water standards (Maximum Contaminant Levels, or MCLs).
Setting Guidance Levels for Drinking Water
As per the Guide to Public Health Goals for Chemicals in Drinking Water, (downloadable PDF), for perchlorate, the California Department of Public Health (CDPH) uses this new determination (among others) to set guidance levels for drinking water. By law, CDPH must set the state’s regulatory standards, Maximum Contaminants Levels (MCLs) as close as possible to the PHG levels that OEHHA establishes. However, CDPH must also consider the cost and technological feasibility of treating or preventing chemical contamination. The OEHHA must also develop a PHG for each drinking water contaminant that is regulated with an MCL or for a contaminant for the first time.
Maximum Contaminant Levels are reviewed by CDPH at least every five years and amended, if necessary, to make them as close to the corresponding PHG as is feasible. The CDPH could amend an MCL if the PHG evaluation indicates that the contaminant is more or less toxic than was previously believed, or if new technology is available to reduce concentrations to levels closer to the PHG.
Is Water Safe to Drink if Contaminant Levels Exceed Public Health Goals?
In general, as long as drinking water complies with all MCLs it is considered safe to drink, even if some contaminants exceed PHG levels. A PHG represents a health‐protective level for a contaminant that CDPH and California’s public water systems should strive to achieve if it is feasible to do so. However, a PHG is not a boundary line between a safe and dangerous level of a contaminant, and drinking water can still be considered acceptable for public consumption even if it contains contaminants at levels exceeding the PHG.
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Determination of Perchlorate in Water
Ion chromatography is a well established technique for the determination of perchlorate and, in fact, the U.S. EPA Method 314.0 (downloadable PDF) was promulgated in 1999 using one of our anion-exchange ion chromatography columns (Thermo Scientific Dionex IonPac AS16 column) and electrolytic eluent generation of hydroxide from distilled water and electrolytic suppression. These electrolytic devices, along with a continuously regenerated trap column, are the main staples of the Reagent Free Ion Chromatography (RFIC) technique.
Since 1999, EPA Method 314.1, and Method 314.2 have been developed for the analysis of perchlorate and both these methods also use the RFIC technique. The U.S. EPA Method 314.2 (downloadable PDF) is a 2-D IC method designed for high matrix, ground water samples, and uses 2 columns with a different chemistry. This approach allows direct injection without sample prep, signal enhancement and elimination of any false positives (downloadable PDF). The EPA has also developed mass spectrometry-based methods for the analysis of perchlorate in environmental waters including one for the analysis of solid waste.
Do check out our Environmental Community which is a wonderful resource that is totally dedicated to our environmental and ion chromatography solutions and features the latest on-demand webinars, videos, application notes, and more.
You might also want to check out our Water Resources webpage has many downloadable articles, white papers, and links to on-demand webinars on water analysis.
If perchlorate analysis is of interest to your laboratory we would like to hear about your thoughts and experiences.