North Carolina researchers are suggesting that the surging increases in type 1
and 2 diabetes
in the United States may be attributed less to genetics than to environmental factors.
Reporting in the December 2001 issue of Environmental Health Perspectives, Matthew P. Longnecker and Julie L. Daniels of the epidemiology branch of the National Institute of Environmental Health Sciences in North Carolina estimate that genetic factors may account for less than half of new cases of type 1 and 2 diabetes.
Longnecker and Daniels cite recent data suggesting that toxic substances in the environment, other than infectious agents or exposures that stimulate an immune response, are associated with the occurrence of diabetes. For example, they found that, for type 1 diabetes
, higher intake of nitrates, nitrites, and N-nitroso compounds as well as higher serum levels of polychlorinated biphenyls have been associated with increased risk (although they note that, overall, the data has been "limited or inconsistent").
According to government
documents, nitrates, nitrites and N-nitroso compounds can be found in cured meat products and some fish, as well as in the general environment and during some manufacturing processes, such as those used in the tanning and tire industries.
Polychlorinated biphenyls (PCBs) formerly were used as coolants and lubricants in transformers and other electrical equipment. Manufacture of PCBs was stopped in 1977, but the compound is still present in the environment.
Longnecker and Daniels write that data on the relationship of arsenic and 2,3,7,8-tetrachlorodibenzo-p-dioxin and the risk of type 2 diabetes
suggests a direct association but is inconclusive.
"The occupational data suggested that more data on exposure to N-nitroso compounds, arsenic, dioxins, talc, and straight oil machining fluids in relation to diabetes would be useful."
Longnecker and Daniel add that environmental factors other than contaminants may also account for the majority of type 1 and type 2
diabetes and should be studied further.