Biomonitoring

Introduction
Biomonitoring is a powerful new tool and an emerging field of scientific research which, if appropriately conducted and interpreted, can provide important exposure information for regulators and public health officials. Chlorpyrifos is a widely used pesticide, and recent studies by the United States Centers for Disease Control (CDC) have reported that biomonitoring has detected in the urine of test subjects extremely low levels of biomarkers associated with exposure to chlorpyrifos. These levels are hundreds of times lower than levels that cause adverse health effects in laboratory animals, as determined by United States Environmental Protection Agency (EPA) and other regulatory bodies.

Dow AgroSciences is committed to our continued work with government scientists and physicians to interpret this data and ensure the safe use of our products.

Background
Biomonitoring is the assessment of human exposure to chemicals, both natural and synthetic, by measuring chemicals or their metabolites in bodily tissues or fluids such as blood or urine.

While scientists have long understood that our bodies absorb trace amounts of various substances simply by living, modern science now allows researchers to detect and measure trace concentrations of increasing numbers of substances within the body. However, by itself, biomonitoring only provides a snapshot of a given chemical's presence or absence in the body at a single point in time.

Some activists attempt to misuse biomonitoring data and relate presence in the body at any level to an unacceptable health risk, and this has generated controversy and irresponsibly elevated public concern

Position
Dow AgroSciences supports the use of scientifically designed biomonitoring studies as a way to help us understand the exposure of humans to chemicals (including pesticides). However, we believe that without context, information on the mere presence of a substance in the body is of little help to people or health professionals. To draw a conclusion about any connection to adverse health effects or disease, the levels of pesticides found must be compared to levels known to cause toxicity or adverse health effects in laboratory studies, which are available in the pesticide registration packages.

It is important to underscore the position of the Center for Disease Control (CDC) which stated in a January, 2003 report:

"Just because people have an environmental chemical in their blood or urine does not mean that the chemical causes disease. The toxicity of a chemical is related to its dose or concentration. Small amounts maybe of no health consequence, whereas larger amounts may cause disease. Research studies ... are requested to determine which levels of a chemical may cause disease and which levels are of negligible health concern."

Chlorpyrifos is widely used, particularly to protect food crops from pests, and recent studies conducted by the CDC demonstrate that the general population is exposed to it at levels hundreds of times lower than those that cause health effects in laboratory animals, as determined by EPA and other regulatory bodies.

When people are exposed to chlorpyrifos, the product breaks down readily and is eliminated from the body in a matter of days. Chlorpyrifos primarily breaks down both in the environment and in people to 3,5,6-trichloro-2-pyridinol (TCP). TCP is easily detected in urine and is considered a biomarker, or surrogate, for exposure to several closely related chemicals, including chlorpyrifos, and TCP is what the CDC measures in its biomonitoring of people. EPA has concluded that levels of TCP to which people are exposed are not of toxicological concern.

Biomonitoring data for TCP has been used in both exposure assessment and epidemiology studies. These data have also been extensively discussed and considered in regulatory evaluations of chlorpyrifos by the EPA and regulatory authorities in other countries charged with protecting public health and safety. Since the presence of TCP in people could be from a variety of pathways, of which exposure to chlorpyrifos is only one, caution must be used when interpreting TCP biomonitoring results.

Key Points – Chlorpyrifos and Biomonitoring

  • Dow AgroSciences supports chlorpyrifos products for all labeled and registered uses. Regulatory agencies such as the EPA along with similar agencies in all other countries determine where and how products containing chlorpyrifos can be used, and exposures to the product are well characterized and understood.
  • Chlorpyrifos has been widely used and extensively studied for almost 40 years. Manufacturers continue to update those tests with new technology each year. Its worldwide registrations are supported by an extensive proprietary and published database. Like all pesticides its uses are tightly regulated by government agencies charged with protecting public health and safety.
  • No other pest control product has been researched more thoroughly. More than 3,600 studies and reports have been conducted examining chlorpyrifos in terms of human health and the environment, including data reviews of its environmental fate, ecotoxicology, neurotoxicity and dietary exposure, plus expert panel reviews assessing the compound's human health and ecological profile.
  • When people are exposed to chlorpyrifos – and trace-level exposures are not unexpected, given the frequent use of the product to protect food crops - the product breaks down readily and is eliminated from the body in a matter of days. That's why the breakdown products are often found in urine: exposures to trace residues are common and the body rapidly processes and eliminates them.
  • Activists have claimed that the exposures that people have to chlorpyrifos as reported by CDC exceed EPA's standards for long-term exposure. However, this activist interpretation of the data is inconsistent if you compare the CDC data with EPA conclusions. These claims by activists are based on an unexpressed assumption that all TCP found in urine derives from exposure to chlorpyrifos. However, when chlorpyrifos is used on crops, it breaks down in the environment to TCP, which is essentially nontoxic, and there are also other ways in which people can be exposed to TCP without exposure to chlorpyrifos, a fact that is clearly recognized in EPA's evaluations of the product. Even if we were to accept this activist interpretation of TCP data at face value, however, chlorpyrifos exposures would still be hundreds of times lower than levels that cause adverse effects in laboratory animals, as determined by EPA and other regulatory bodies charged with the protection of public health.
  • When put in proper context by relating to other toxicological information, biomonitoring data are important in helping public health and regulatory officials understand the extent to which people have been exposed to particular substances and may provide guidance for additional research. However, it is important to note that biomonitoring data does not indicate the source of an exposure; how long a substance has been in the body; and what effect, if any, a substance may have on human health.
  • It is regrettable that activists are misrepresenting data issued by the CDC and creating confusion among people and health professionals. Dow AgroSciences is committed to continue our work with government scientists and physicians to interpret this data and ensure the safe use of our products.