GILROY
– Studies reveal that water contaminated with perchlorate at
roughly 245 parts per billion does not affect human health, but
health safety recommendations for levels as low as 1 ppb are still
moving forward by scientists.
GILROY – Studies reveal that water contaminated with perchlorate at roughly 245 parts per billion does not affect human health, but health safety recommendations for levels as low as 1 ppb are still moving forward by scientists.
At various perchlorate-themed meetings in recent days, both state and federal scientists acknowledged that a 2002 study revealed no significant inhibition of iodide uptake in thyroids when the rocket fuel and road flare chemical is given at a dose of 0.007 milligrams per kilogram of body weight.
The 2002 study is the basis for both a federal- and state-level scientific analysis to determine at which level the government should regulate perchlorate contamination in water and food.
Based on calculations for a normal 70-kilogram (154-pound) person, it would take a water source tainted with about 245 ppb of perchlorate to equal the 0.007 dosage. Decreased thyroid function and a higher incidence of thyroid tumors are associated with perchlorate ingestion.
The news about the gap between what is harmful and what scientists suggest to be allowed is surprising to some. But as more and more South County wells – now around 450 – test positive for perchlorate, and as researchers at the defunct road flare factory in Morgan Hill learn the contamination footprint is larger than initially thought, the news is also comforting.
“We’re very fortunate the contamination is as low as it is in this area, and we’re lucky the polluter is doing their part to clean things up,” San Martin activist Sylvia Hamilton said. “The mass population is not being negatively affected, but some people are more sensitive (to perchlorate) than others, and I think state and federal levels should be set conservatively.”
Government officials are working to set, essentially, two types of perchlorate guidelines. One is more stringent and takes into account only the scientific data regarding perchlorate health risks. The other guideline is potentially less stringent because it will be used to regulate perchlorate users, but will factor in what sort of precautionary and cleanup measures are technically and financially possible.
At both the federal and state levels, recommendations for allowable perchlorate levels range from 1 to 6 ppb. Currently, a perchlorate level of 4 ppb triggers warning notices to affected water users.
So why propose 1 to 6 ppb regulatory levels when it’s upward of 245 ppb that is needed to cause damage?
It’s because of uncertainties with the format of the studies themselves, says Kevin Mayer, a regional perchlorate coordinator for the federal Environmental Protection Agency.
The studies being used by government toxicologists to set these regulatory levels tested healthy men and women over a 14-day period.
Results would vary had children, infants, pregnant women and people with unhealthy thyroids been tested. So, government toxicologists factor in a mathematical formula that’s put their perchlorate level recommendation firmly on the safe side.
Ethical considerations prevent scientists from testing sensitive segments of the population.
“We’re in the business of protecting a whole population. When we make a recommendation, we’re taking the whole population into consideration, and we’re trying to be protective,” Mayer said.
At least two law firms have brought nearly 300 suits against Olin Corporation, the company that polluted South County wells. No South County well outside the Morgan Hill factory site has tested at more than 100 ppb.
Richard Alexander, an attorney with one of the law firms bringing the suits, said the difference between suggested levels for perchlorate and the level that actually harms humans won’t affect his cases.
“We are not making health care claims because California law requires you to prove exposure and dose, and we didn’t have people testing this water 20 and 30 years ago,” Alexander said. “All our lawsuits are property damage claims for having turned San Martin into a toxic dump. We’ve never seen so many houses taken off the market because they just don’t sell.”
Meanwhile, concerns continue to rise over news that soil at the factory site is contaminated as deep as 15 feet below the surface.
The depth is troublesome since the water table can rise to 7 feet from the surface, said Harvey Packard, a Regional Water Quality Control Board speaking at a perchlorate advisory group meeting last week in San Martin.
Packard had announced that Olin is proposing to flush contaminated soil and groundwater by using an intricate 225- by 450-square-foot leaching system, instead of a more straightforward cleanup method such as excavation.
“It makes sense to me that Olin wouldn’t excavate the entire site since they’d just be putting their problem somewhere else,” said Farm Bureau Executive Director Jenny Midtgaard Derry. “But I’d still like to see them excavate the hot spots.”
Hot spots are the areas of worst contamination. Derry figures that if these areas are dug up, perchlorate will have a harder time finding its way into the groundwater aquifer.
Agricultural leaders around Santa Clara County have been keeping a keen eye on perchlorate cleanup and studies. Last week, they issued a five-point resolution calling for, among other things, scientific studies showing how much perchlorate resides in a broad range of crops.
Since perchlorate contamination came onto the scene, studies on isolated crops and studies done by backyard experimenters have taken place. Ag leaders want more precise information since results from these tests could severely impact Santa Clara County produce sales.
Derry said the information about a 245 ppb perchlorate level being required to cause an impact to human thyroids was news to her.
“It really doesn’t change my approach or my feeling about this because each crop is going to uptake perchlorate so differently,” Derry said. “We need better information.”
