Focusing on perchlorate standards

Friday, August 08, 2003

By Carol Holzgrafe (carolh@gilroydispatch.com)

SACRAMENTO - It took months to put together, but experts from all across the state and the nation gathered at a seminar in Sacramento last Thursday to discuss perchlorate in groundwater.

The day-long affair covered perchlorate’s health risks for humans, affects on crops, treatment of contaminated water and soil and case studies. It also focused on the appropriate maximum contaminant level (MCL) for perchlorate the state Department of Health Services is scheduled to set by next year, which according to the majority of speakers in attendance will be near 4 parts per billion.

Currently, the California Environmental Protection issues warning notices to affected water users whose perchlorate levels measure 4 ppb or higher, although it is not yet a lawful state regulation.

Since perchlorate testing began in South Valley in January, more than 400 wells between Morgan Hill and Gilroy have tested between 4 and 100 ppb.

“Hearing the experience from other agencies and hearing directly from the EPA and DHS regarding how future levels (of perchlorate) will be set was most valuable,” said Morgan Hill Public Works Director Jim Ashcraft.

Since January when perchlorate was found to have spread to the local underground water system from an initial contamination source at the Olin Corp. roadside flare plant at Tennant and Railroad avenues in south Morgan Hill, South Valley residents have pressed for more information about the chemical.

The seminar was organized and chaired by Thomas Mohr, engineering geologist for the Santa Clara Valley Water District, an agency closely involved with perchlorate’s contamination of wells in north Gilroy, San Martin and Morgan Hill. It was one of a series of such seminars on groundwater contaminants hosted by the Groundwater Resources Association of California, where Mohr is a director.

Robert Howd, chief of the water toxicology unit at the state Office of Environmental Health Hazard Assessment (OEHHA), part of the California Environmental Protection Agency, explained to the audience how perchlorate is measured. Howd’s office evaluates the risks of exposure to chemicals in air, water and soil and sets the Public Health Goal (PHG) for substances in groundwater.

Howd described PHG as the level of contaminant in drinking water that poses no significant health risk to people drinking the water daily for a lifetime. He said the level is determined “without regard to cost or technical feasibility (and) considers sensitive groups” - such as pregnant women and infants - and considers built-up exposure from all sources.

The PHG is advisory only and is not mandatory. Howd said that, even though the United States EPA decided on July 11 not to propose regulations for perchlorate in drinking water, the OEHHA expects to set the perchlorate PHG by fall.

David Ting, Ph.D., also of Howd’s agency, explained methods of varying testing of the effect perchlorate has on thyroid function. Perchlorate is known to inhibit the uptake of iodide to the thyroid gland. He recommended a level of 2 ppb.

David Spath, chief of the Division of Drinking Water and Environmental Management for the California Department of Health Services, said the MCL is usually as close to the PHG as possible. He said a zero level - no perchlorate at all - is impossible to work with, and suggested that 2 ppb would protect fetuses and infants.

Spath said more than 400 public water system wells in California show levels of the chemical between 4 ppb and 300 ppb.

Spath announced that the draft PHG will likely suggest levels of 2 ppb for infants and 6 ppb for adults.

“Right now my laboratories feel 4 ppb is reasonable,” Spath said. “... We didn’t react early enough (to the perchlorate issue). We knew in the early 1980s that it was a contaminant and we weren’t conservative enough in toxicology. In the future, we will react faster.”

In evaluating the PHG, Spath’s agency is required to look at the technical feasibility of regulating perchlorate, including laboratories’ ability to analyze for low levels, the costs of monitoring and the costs of cleanup.

He said the draft PHG is under review by the University of California.

* The draft review of PHG is available at www.oehha.ca.gov/water/phg/120602perchlorate.html

* The draft PHG is available at www.dhs.ca.gov/ps/ddwem/

* OEHHA: www.oehha.ca.gov/water/phg/index.html; GRA: www.grac.org