By Pat Rizzuto
Concentrations of bisphenol A and methyl tertiary butyl ether (MTBE) in individuals have decreased since the Centers for Disease Control and Prevention (CDC) first released a report in 2001 documenting levels of industrial chemicals, metals, and pesticides in the U.S. population.
Concentrations of urinary perchlorate have generally increased in that time, CDC found.
The picture for other compounds, such as metabolites of organophosphorus insecticides, is more complicated, with concentrations of some metabolites decreasing and others increasing.
CDC's Division of Laboratory Sciences released the updated data online Sept. 26 for its Fourth National Report on Human Exposure to Environmental Chemicals.
That report is an ongoing assessment of the U.S. population's exposure to environmental chemicals. The new information updates biomonitoring data released in 2009 by CDC (33 CRR 1219, 12/14/09).
The Fourth Report provides data on the U.S. population's exposure to 212 chemicals. CDC's report does not draw any conclusions about the health effects of the exposures, stressing that “the presence of an environmental chemical in a person's blood or urine does not necessarily mean that it will cause effects or disease.”
CDC first measured urinary concentrations of bisphenol A, also known as BPA, as part of its 2003-2004 National Health and Nutrition Examination Survey (NHANES). At the time, the geometric mean for the population was 2.64 micrograms per liter (µg/L). In the 2009-2010 survey, the geometric mean was 1.83 µg/L.
CDC groups its measurements into categories of age, gender, and race or ethnicity.
Among those groups, non-Hispanic blacks experienced the greatest decrease with the concentration of urinary bisphenol A at the 95th percentile being 20.6 µg/L in 2003-2004 and dropping to 10.3 µg/L in 2009-2010. The 95th percentile means that approximately 95 percent of the U.S. population has concentrations below that level.
Bisphenol A is used to make polycarbonate plastic, which is used in beverage containers, compact disks, impact-resistant safety equipment, automobile parts, toys, and other products, CDC said in its Fourth Report. BPA epoxy resins are used as protective linings in food cans, dental sealants, and other products, the agency noted.
The geometric mean of MTBE in people's blood dropped from 16.4 picograms per milliliter (pg/mL) in 2001-2002 to 6.16 pg/mL in 2005-2006.
The concentrations at the 95th percentile of Mexican Americans dropped the most during those years, from 273 pg/mL to 100 pg/mL. However, the level at the 95th percentile for non-Hispanic blacks increased from 120 pg/mL to 180 pg/mL.
MTBE was used as an additive in reformulated gasoline to boost octane and reduce air pollutants beginning in the late 1970s and continuing into the 2000s before concerns about its potential to contaminate drinking water supplies led to bans or restrictions in several states.
Concentrations of urinary perchlorate have generally increased since CDC first began measuring them in 2001.
The geometric mean for the population increased from 3.72 µg/L in 2001-2002 to 3.88 µg/L in 2007-2008.
The concentrations increased over that time span within most age, gender, and racial groups. However, concentrations decreased in children ages 6 to 11. Their geometric mean dropped from 5.19 µg/L to 4.88 µg/L. Perchlorate is both naturally occurring and synthetic. Its manufactured uses include fireworks and matches, with limited applications in pharmaceuticals, laboratory analysis, leather tanning, fabric dyeing, and electroplating, CDC said.
Organophosphorus insecticides are a large family of pesticides including azinphos methyl, chlorpyrifos, dichlorvos, diazinon, malathion, and methyl parathion. CDC measures six metabolites found in urine that are produced by several organophosphates.
The concentrations of four of these metabolites generally increased among nearly all groups CDC measured, while levels for the other two generally decreased.
Margaret Reeves, a senior scientist with Pesticide Action Network, told BNA Sept. 28 that the decrease likely can partly be attributed to the Environmental Protection Agency's decision in 2000 to restrict virtually all home uses of chlorpyrifos (24 CRR 1173, 6/12/00).
Without knowing more about the occupational exposures that occurred in the populations CDC measured, the times of year in which the measurements were taken, or the locations of the country in which they were taken, it is difficult to tease out conclusions for much of the data, Reeves said.
However, most of the policy recommendations Pesticide Action Network made in 2004 when it released a report Chemical Trespass still apply, she said.
Those include urging EPA to ban pesticides known to build up in people's bodies, and urging pesticide manufacturers to develop analytical methods to measure pesticides and metabolites in people's bodies.
CDC's updated Fourth National Report on Human Exposure to Environmental Chemicals is available at http://www.cdc.gov/exposurereport/pdf/FourthReport_UpdatedTables_Sep2012.pdf.