Authors
Cantor KP, Strickland PT, Brock JW, Bush D, Helzlsouer K, Needham LL, Zahm SH, Comstock GW, Rothman N.

Title
Risk of non-Hodgkin's lymphoma and prediagnostic serum organochlorines: ss-hexachlorocyclohexane, chlordane/heptachlor-related compounds, dieldrin, and hexachlorobenzene.

Journal
Environmental Health Perspectives; 2003;111(2):179-84.

Summary
Incidence of non-Hodgkin's lymphoma (NHL) and associated mortality have increased in the US and in other countries in the past 30-40 years. This increase in the disease has been ascribed to use of immunosuppressive drugs, increasing rates of HIV infections among other factors, however, many cases have an unexplained etiology. Exposure to organic solvents, pesticides and other chemicals has been correlated with increased NHL risk in case-control and other studies. In one hospital-based case-control study, that serum chlordane and related compounds were associated with NHL risk, while other population-based case-control studies have linked NHL to self-reported agricultural exposure to organochlorine pesticides. In the present study, Cantor et al. investigate the association of serum organochlorine compounds with NHL risk.

This nested case-control study matched cases, identified from the Washington County Cancer Registry, with two controls for each case. 'Cases' had a confirmed diagnosis of NHL, no history of cancer prior to diagnosis and serum samples (prediagnosis) available for analysis. Controls had no history of cancer and were matched on the basis of race, sex, date of birth within one year and stored serum for analysis. Organochlorines measured included: lindane-related compounds [lindane ( -hexachlorocyclohexane) and ( -hexachlorocyclohexane), four chlordane or heptachlor-related compounds ('chlordane/heptachlor': transnonachlor, heptachlor, heptachlor epoxide, oxychlordane), two aldrin-related compounds (dieldrin and endrin), hexachlorobenzene, mirex, four DDT-related compounds and 28 PCB congeners. All values were corrected to total serum lipids.

This study found no association between any of the chemicals measured in prediagnostic serum and NHL. These findings contradict previous studies suggesting that organochlorine compounds are linked with increased risk of NHL. This study has many strengths; the nested case-control design, the use of stored sera for analysis, thereby eliminating differential bias and correction for serum lipids. Negative results should be carefully interpreted. It is possible that confounding factors were not considered. It is also possible that lipid-correction of the chemical values may have contributed to the negative findings. Many compounds analyzed in this study have been previously identified as carcinogens in animal bioassays, with the epidemiological evidence, although weak, suggestive that these organochlorine compounds may also be carcinogenic in humans and linked to NHL. Many of these chemicals have been suggested to act as endocrine toxicants and have been linked to other human health concerns. The authors did not discuss the biological mechanism by which these organochlorine chemicals would cause NHL. NHL has been linked with Epstein-Barr virus, which in turn has also been suggested to be associated with organochlorine exposure. Further investigation into the etiology of NHL, the risk factors associated with organochlorine exposure and the biological mechanism by which exposure to these compounds may result in disease is required.