Thursday, April 8, 2010

Your Chemical Exposure

Chemicals are everywhere, they exist in pharmaceuticals, household products, personal care products, plastics, pesticides, industrial chemicals, human and animal waste; they are in short, all around us. According to the Toxic Substances Control Act (TSCA) inventory of chemicals there are more than 84,000 chemical substances, as defined in TSCA today. These chemicals include organics, inorganic, polymers, and UVCBs (chemical substances of Unknown or Variable composition, Complex reaction products, and Biological materials). According to poll of 2,016 British women by deodorant-maker Bionsen, the typical woman applies 515 chemicals daily to her body between perfume, soaps, shampoos, styling lotion, skin lotions, face creams, makeup, and the list goes on. This may or may not be alarming, because these chemicals are applied to the skin and need to pass the barrier to become bioavailable, but it is certainly an indication of how pervasive chemicals are in our lives.

In December the Center for Disease Control released their most recent National Report on Human Exposure to Environmental Chemicals. Thought the report was incomplete at the time of release, it is the most comprehensive assessment to date of the exposure of the U.S. population to chemicals in our environment. CDC measured 212 chemicals in the blood and/or urine of the participants. The samples were collected from participants in CDC's National Health and Nutrition Examination Survey (NHANES), which is an ongoing survey that samples the U.S. population every two years. Each two year sample consists of about 2,400 people. What the report found was Widespread Exposure to Some Industrial Chemicals throughout the population tested. The implications of this ubiquitous exposure are unknown, but of concern. The detection of a chemical in people's blood or urine does not mean that it will cause health effects or disease. It has been believed for hundreds of years that the toxicity of a chemical is related to its dose, in addition to a person's individual susceptibility. The philosophy that small amounts were of no health consequence has been the cornerstone of toxicology and regulation, but that has recently come into question. For most of the environmental chemicals included in the CDC Report, more research is needed to determine whether exposure at the low levels reported is a cause for health concern.

Findings in the Fourth National Report on Human Exposure to Environmental Chemicals indicate widespread exposure to some commonly used industrial chemicals. This exposure may not be new, per sea but our ability to identify parts per trillion has opened the door to a raft of concerns and questions. Though you might want to read the entire report or just the executive summary, I’ve included some highlights.

Polybrominated diphenyl ethers are fire retardants that accumulate in the environment and in human fat tissue. One type of polybrominated diphenyl ether, BDE-47, was found in the serum of nearly all of the NHANES participants.
Bisphenol A (BPA), a component of epoxy resins and polycarbonates, and a potential endocrine disruptor was found in more than 90% of the urine samples of the participants.
Another example of widespread human exposure included several of the perfluorinated chemicals. One of these chemicals, perfluorooctanoic acid (PFOA), is a byproduct from the manufacture of polytetrafluoroethylene, which is used to create non-stick coatings in cookware. Most participants had measurable levels of this contaminant.
The gasoline additive methyl tert-butyl ether (MTBE) has been eliminated in gasoline formulations, but a high percentage of the NHANES participants showed detectable levels of MTBE.
The chemical perchlorate is both naturally occurring and manmade and is used to manufacture fireworks, explosives, flares, and rocket propellant. For decades, scientists have known that large doses of perchlorate affect thyroid function. Low-level exposure to perchlorate from the environment has been under investigation in recent years. All NHANES participants were found to have detectable perchlorate in their urine.
Total blood mercury levels, primarily composed of methyl mercury, which enters the body mainly from dietary seafood sources. Findings show that total blood mercury levels increase with age for all groups and begin to decline after the fifth decade of life.
A big bright spot in the report was the continued decline in Lead levels in blood.

Many questions were raised by the CDC data, one that has not been fully addressed is the route of exposure. The CDC believes that for most chemicals, people are exposed to low levels through foods or by breathing in air that contains the chemical or consuming water, plants or animals that contain the chemical. The CDC suggests that MBTE could have potentially contaminated water sources. I have seen perchlorate as a groundwater contaminant all over California during site investigations. People can also be exposed by using products with chemicals in them or which have been stored in containers made with the chemicals. The Agency for Toxic Substances and Disease Registry (ATSDR), the National Institute of Environmental Health Sciences (NIEHS), and the U.S. Environmental Protection Agency (EPA) sponsor research that addresses sources and effects of chemical exposures. The EPA has recently launched investigations into BPA and other endocrine disruptors.

Endocrine disruptors are a class of chemicals that can mimic, block, or otherwise alter animal hormone responses, sometimes affecting their reproduction, development, and behavior, this is actually, how some pest control treatments are designed to work. A diverse group of chemicals called endocrine disrupting chemicals (EDCs) come from a variety of sources. These chemical have diverse molecular structures. BPA is just one of these chemicals. These chemicals become of great concern when they are discovered to be potential human endocrine disruptors as DDT, dioxin, the drug DES and PCBs were in the past. Traces of endocrine disrupting chemicals are seemingly found in every part of our world, including dust, soil, water, air, food, manufactured products, wildlife, and even ourselves. So, as congress considers revising the Toxic Substances Control Act, EPA and NIEHS begin their investigations into endocrine disruptors.

No comments:

Post a Comment