Body burdens – new ground 

With almost identical timing, two new reports from the United States (US) reinforce growing concerns with chemical body burdens.

The US government’s Centers for Disease Control (CDC) National Health and Nutrition Examination Survey (NHANES), is conducted across a statistically valid sample of people, around 2,000, and uses biomonitoring techniques to assess indicators of public health, including exposure to environmental chemicals. The NHANES provides crucial baseline data against which it is possible to detect trends, the minimum information needed in assessing how much of a disease burden, for example, chemical contaminants are causing.
    CDC’s first such national report, on 27 chemicals, was issued in March 2001. This latest report, released in January 2003, presents blood and urine levels of 116 environmental chemicals from a sample of the population, by age, sex and ethnicity, during the two-year period, 1999-2000. The CDC’s analysis, which does not draw conclusions about the overall health impacts of multiple chemical residues, aims to:

• assess exposure levels to 116 environmental chemicals
• for each chemical with a known toxicity level, determine the prevalence of people with levels above that toxicity level
• establish reference ranges that can be used by physicians and scientists to determine whether or not a person or group of people has an unusually high exposure

One notable findings is that levels of DDT metabolites are detectable in the blood of 12-19 year olds who were born after DDT was banned for use in the US.
    The Environmental Working Group report, examines the overall body burden of around the same number of chemicals, including 32 pesticides, in nine individuals. Their report is a fierce indictment of the widespread contamination of people perpetrated by the chemical industry, allowed by government regulators. 
    The study is limited principally by cost: 

• each laboratory investigation cost $4,900
• the need to select by guesswork a number of common chemicals and pesticides from the vast number in use 

The detailed expertise in this report picks out flaws in the science, policy, and regulation of chemicals. For example, the authors note that mandated test methods are sometimes orders of magnitude less sensitive than those developed by leading laboratories. A section of the report entitled ‘Low doses can hurt you’ challenges the assumption, that ‘the toxicity of a chemical is related to its dose or concentration ... Many of the exposures reported here are below the levels thought to be toxic in standard high dose toxicology studies relied upon by industry and regulators. The government’s historic dependence on high dose studies has created an institutional and scientific bias that encourages regulators and industry to assert, with little supporting data, that low doses like those reported here cause no adverse effects.
    ‘… Chemical toxicology today falls into two camps: regulatory toxicology, where scientists generally in the pay of chemical companies, conduct high dose animal studies under prescribed protocols for the purpose of meeting government requirements; and research toxicology, primarily conducted at independent university and government research centers, where scientists focus on low dose exposures to chemicals that lead to harmful effects on the body.’
    These reports will encourage regulators to increase resources for urgently needed surveys: both statistically valid, such as NHANES, and more in-depth analyses of overall body burdens. (AC)

References
1. Centers for Disease Control and Prevention, Department of Health and Human Services, Second national report on human exposure to environmental chemicals, January 2003 www.cdc.gov/exposurereport
2.Houlihan, Jane et al, Body Burden – the pollution in people, Environmental Working Group, www.ewg.org

[This article first appeared in Pesticides News No. 59, March 2003, page 21]