This article was submitted by Dr. Richard Cassidy and was not written by Diabetes Health.

Obesity has been accepted as a risk factor for diabetes, but the results of four recently published studies have now revealed that insecticides in fat may be the real risk factor. The initial investigations showed that the expected association between obesity and diabetes/insulin resistance was absent in people who had low levels of organochlorine insecticides in their blood (1, 2). However, the expected association between obesity and diabetes/insulin resistance increased as these insecticides levels increased.

In the last few months, two additional studies have linked these insecticides with diabetes (3, 4).  In all four studies, the insecticides consistently having the greatest association with diabetes were compounds of the chlordane family (oxychlordane, trans-chlordane, trans-nanochlor, and heptachlor).

One way these chlordane compounds may cause insulin resistance and diabetes is by their pro-oxidant effects.  Several studies have indicated that oxidants damage cells that produce insulin and induce insulin resistance (5).  The author of this article has reported that a chlordane compound, at levels found in U.S. citizens, increases oxidant production and causes cellular damage in white blood cells isolated from human blood (6).

All of these insecticides are in the same class of organochlorines, called cyclodienes, first made in the 1940s.  Their development was by chance, during a search for possible uses of a byproduct of synthetic rubber manufacturing.  By chlorinating this byproduct, persistent and potent insecticides were easily and cheaply produced. The chlorines, seven in the case of heptachlor and eight in trans-chlordane, oxychlordane, aldrin, and dieldrin, surround and stabilize the cyclodiene ring (the carbon skeleton). 

These cylodienes, all members of the “Dirty Dozen”, are still found in food, especially animal fat, and in indoor air of homes treated for termites prior to the ban of chlordane/heptachlor in 1988.  Breathing these vapors is the main route of exposure for occupants of treated homes, with exposure levels approximately 25 times the levels ingested in food (7).  Body levels accumulate with the age of the occupant.  The adverse public health effects of breathing these insecticides are under-appreciated, considering that 30 million homes were treated with chlordane/heptachlor.

In a recent study conducted in Cape Cod, Massachusetts, tests for hormone-disrupting chemicals in indoor air detected chlordane, heptachlor, and/or dieldrin in 50 to 60 percent of the homes, with levels four to 40 times the U.S. Environmental Protection Agency (USEPA) guidelines.  Because termite infestation and treatment increase in warmer climates, these numbers should increase in homes located farther south. Depending on the location of treatment in the home, the indoor air concentrations can vary in orders of magnitude. High levels of chlordane and heptachlor (200-2000 ng/M3 (1 ng/ M3 is equal to one/billionth gram per cubic meter of air)) are found when treatment was beneath the home, under the basement floor, in the soil of an enclosed crawl space, or under concrete slab floors.

Persons living in homes built prior to 1990 and in the southern three-quarters of the United States are most at risk of breathing these insecticides. Breathing these insecticides or having insecticides in human tissues is linked to a variety of symptoms (headache, lethargy, upper respiratory infections), human cancers (prostate, breast, testicular, leukemia, lymphoma), and chronic diseases (insulin resistance, diabetes, depression, Parkinson).

Owners of treated homes could increase their exposures after energy saving renovations.  Applying additional insulation may increase indoor air concentrations of chlordane compounds by reducing air infiltration. Using basements as living spaces is of special concern and can result in exposures five to eight times those in ground floor rooms. 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 living space.  Heat-exchange ventilation systems have been shown to markedly reduce levels of chlordane in homes.  Most major heating/air conditioning manufacturers offer these systems, and they can be easily interfaced to current ducting system.

Considering the effects of diabetes on the individual and the economic well-being of our nation, increasing public awareness of the health risks of breathing chlordane in the air of homes is vital.

If you have questions, email Dr. Cassidy at racassidy@psci.net or call 888.836.4489. 

Read a list of Dr. Cassidy’s publications on chlordane health effects and his bio.

References:

1.    D. Lee, et al. (2006). A strong dose-response relationship between serum concentrations of persistent organic pollutants and diabetes. Diabetes Care.  29:1638-1644.

2.    D. Lee, et al. (2007). Association between serum concentrations of persistent organic pollutants and insulin resistance among nondiabetic adults. Diabetic Care. 30: 622-628. 

3.    S. Cox, et al. (2007).  Prevalence of self-reported diabetes and exposure to organochlorine pesticides among Mexican Americans: Hispanic health and nutritional examination survey, 1982-1984. Environmental Health Perspectives. 115:1747-1752.

4.    M. P. Montgomery, et al. (2008).  Incident diabetes and pesticide exposure among licensed pesticide applicators: Agricultural health study, 1993-2003.
American Journal of Epidemiology Advance Access published March 14 2008.  http://aje.oxfordjournals.org/cgi/content/abstract/kwn028v1.

5.    N. Houstis, et al. (2006). Reactive oxygen species have a causal role in multiple forms of insulin resistance. Nature. 440:944-948.

6.    R. A. Cassidy, et al. (2005). The link between the insecticide heptachlor epoxide, estradiol, and breast cancer. Breast Cancer Research and Treatment. 90:55-64.

7.    U.S. Environmental Protection Agency. (1990). Nonoccupational pesticide exposure study (NOPES) EPA 600/3-90-003. NTIS no. PB90-152224.