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Air Testing and Consulting
Dr. Richard A. Cassidy

6160 St. Joe Cemetery Road - Tell City, IN 47586

in 1996

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Chlordane: An Under-Appreciated Indoor Health Risk

Home, Health, and Happiness

All of us have lived or are currently living in homes built before 1988. Over 30 million of these homes were treated for termites with chlordane, an insecticide that was banned in 1988. Chlordane (technical) is a mixture of compounds that are stable in the dirt beneath our homes and de-gas at a constant rate thru cracks in floors and walls, and in openings around pipes. As we inhale these vapors our livers convert these insecticides to more potent carcinogens and toxins (oxychlordane, heptachlor epoxide and dieldrin) that accumulate in our fat. The air concentration of chlordane compounds in our current and previous home will determine the amount of oxychlordane, heptachlor epoxide and dieldrin in our body. Chlordane compounds do not damage cells directly by reacting with molecules but instead by binding to receptors of steroid hormones (hormone disruptors), especially estrogen receptors. These estrogen receptors regulate many processes in many organs of the body. Estrogen receptors are located throughout the human brain and scientists have known for years that chlordane causes anxiety, depression, and behavioral, cognitive, and memory deficits. Chlordane also disrupts estrogen receptors in reproductive organs and reduces fertility.

Recent studies demonstrate that chlordane compounds bind to estrogen receptors on human immune cells inducing production of oxidants that damage cellular structures such as DNA and initiate chronic inflammation. These chronic inflammatory processes ultimately may cause insulin resistance, diabetes, respiratory infections, and possibly organic brain damage such as Parkinson disease.

In animal studies, chlordane compounds have been determined to be some of the most potent carcinogens. Chlordane compounds in humans have been linked to increased rates of breast, prostate, testicular, leukemia, lymphoma, and brain cancer.

All of these insecticides are in the same class of organochlorines called cyclodienes first made in the 1940s by Julius Hyman. Their development was by chance, during a search for possible uses of a by-product of synthetic rubber manufacturing. By chlorinating this by-product, persistent and potent insecticides were easily and cheaply produced. The chlorines, 7 in the case of heptachlor and 8 in chlordane, aldrin, and dieldrin, surround and stabilize the cyclodiene ring. These cylodienes, all members of the “Dirty Dozen”, are still found in indoor air of homes 30-40 years after treatment. Breathing these vapors is the main route of exposure and body levels accumulate with the age of the occupant.

In 2003, tests for hormone disrupting chemicals conducted in Cape Cod, Massachusetts detected chlordane, heptachlor, or dieldrin in the air of 50-60% of the homes with levels 4-40 times the US Environmental Protection Agency (USEPA) risk-based guidelines for ambient air. Since termite infestation and treatment increase in warmer climates, these numbers would increase with homes located farther south (see www.toxfree.net for map).

Depending on the location of treatment in the home, the indoor air concentrations can vary orders of magnitude. High levels of chlordane and heptachlor (200-2000 ng/M3, ng/ M3 is equal to one/billionth gram per cubic meter of air) are found when treatment is beneath the home – under the basement floor, in the soil of an enclosed crawl space, or under concrete slab floors.

The risk of adverse effects from these insecticides is based on indoor air concentrations. The risk-based guidelines for minimal cancer risk published by the USEPA, and the No Observable Effect Levels (NOEL) for non-cancer effects published by the Agency for Toxic Substances and Disease Registry are approximately the same, 5-10 ng/M3. For most people, except chemically sensitized individuals, exposure below these levels should pose only a minimal risk. Adequate indoor air testing requires measuring at or below 5 ng/M3 for these cyclodienes.

Indoor air testing for these insecticides is recommended for person buying homes built prior to 1990 and for persons living in older homes who are experiencing symptoms linked to these insecticides (see When You Should Test in www.toxfree.net. Basements used as living spaces are of special concern and can have levels 5 to 8 times those in the rooms on the ground floor. Patched drill holes in the concrete basement floor, usually next to the walls, are red flags, and should warn occupants that basements should be tested before being used as a living space.

I have tested the levels of chlordane/heptachlor and aldrin/dieldrin in the indoor air of hundreds of homes during the last decade. Comparing insecticide exposures and symptoms of these clients, it appears that these insecticides cause symptoms that are usually seen in persons 5-20 years older than the age of the clients. This observation is supported by a recent study indicating that women with higher chlordane blood levels experience symptoms of menopause, on average, over 5 years earlier than normal.

Two ways to remove these chlordane vapors from the air in your home is by ventilation with outside air or filtering indoor air through activated charcoal. Most major heating/air conditioning manufactures offer heat-exchange ventilation system that can be easily interfaced to your current ducting system. I have tested homes before and after such installation and have found at least a 10-fold reduction in the levels of insecticides.

For persons living in chlordane/heptachlor and/or aldrin/dieldrin treated homes, breathing these insecticides has the potential of causing greater adverse health effects than other more widely publicized pollutants. For more information on health effects and air testing see (www.toxfree.net). Dr. Cassidy provides free consulting and would be happy to answer your questions, email me or call 812.719.1163.


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