Last month on page 4, I questioned whether the dispute over how to best deal with perchlorate would be able to avoid becoming an unduly raucous and mud-spattered affair. It's likely we'll be getting a good indication in short order as the U.S. Environmental Protection Agency (EPA) has gone ahead and established an official reference dose (RfD) of 0.0007 mg/kg/day of perchlorate. This level is consistent with the recommended reference dose included in the National Academy of Science's (NAS) January 2005 report. A reference dose is a scientific estimate of a daily exposure level that is not expected to cause adverse health effects in humans.
EPA says its reference dose, which assumes total intake from both water and food sources, is appropriate and protective for all populations, including the most sensitive subgroups. The selected reference dose contains a tenfold uncertainty factor to protect the most sensitive population, the fetuses of pregnant women who might have hypothyroidism or iodide deficiency. This uncertainty factor also covers variability among other human life stages, gender and individual sensitivities.
Perchlorate exposure has the potential of blocking iodide uptake to the thyroid gland. NAS identified the non-adverse effect of the inhibition of iodine uptake as the key biochemical event that precedes the occurrence of all potential adverse effects of perchlorate exposure. EPA claims that its RfD is conservative and health protective because it is designed to prevent the occurrence of any biochemical changes that could lead to adverse health effects.
The reference dose for perchlorate will be posted on the agency's online IRIS database, which contains risk information on possible human health effects from exposure to chemical substances in the environment. Visit .
This new RfD translates to a Drinking Water Equivalent Level (DWEL) of 24.5 ppb. A DWEL, which assumes that all of a contaminant comes from drinking water, is the concentration of a contaminant in drinking water that will have no adverse effect with a margin of safety. Because there is a margin of safety built into the RfD and the DWEL, exposures above the DWEL are not necessarily considered unsafe.
Consumer Filtration MarketThe good folks from Mintel International Group recently completed some hard-core number crunching on the domestic water filtration market. Some highlights:
Mintel's researchers tell us that the $1.6 billion consumer market for water filtration products grew 28 percent over the review period of 1998-2003, although growth slowed substantially since 2000. While concern with health and water quality spurred growth, competition from bottled water and residential systems installed by professionals (not included within the scope of this report) carved into the consumer market. Continued trends towards healthy lifestyles and the concerns of aging adults should maintain positive, though moderate, sales growth through 2008.
You can purchase a copy of the complete 88-page report by visiting www.mindbranch.com.
Johnson Tabbed for EPA PostPresident Bush has promoted Stephen Johnson from temporary-acting head of the U.S. Environmental Protection Agency (EPA) to an officially nominated leader for the agency.
Johnson, a career government employee who has been with the agency for 24 years, had been acting in his role as the agency's leader for almost two months.
“He knows the EPA from the ground up and has a passion for its mission,” Bush said at the announcement. If confirmed by the Senate, Johnson would become the first professional scientist to head the agency and would be its 11th administrator.
Johnson's predecessor, Michael Leavitt, now is serving as the secretary of Health and Human Services.
Bush says one of Johnson's top responsibilities would be to “lead federal efforts to ensure the safety of our drinking water supply,” saying the EPA has “an important role in the war on terror."