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Epidemiology November 1997, Volume 8 Number 6 EPIDEMIOLOGY AND THE INTERNET 689 Polychlorinated Biphenyls, Chlordanes, and the Etiology of Non-Hodgkin's Lymphoma To the Edtm During the last few decades, non-Hodgkin's lymphoma (NHL) has heen one of the most rapidly increasing types of cancer in the Western world. During the period 1958-1992, the mean age-acijusted incidence increased yearly by 3.6% in men and 2.9% in women in Sweden.` In investigations' NHL has been associated with exposure to phenoxy herbicides, chlorophenols, or organic solvents.?.' Phenoxyacetic acids and chlorophenols may be Mats Fredrikson Department of Occupational and En\ironmental Medicine. UniLersity Hospital. Linkoping, Suecfen Hans Hagberg of Oncology, Akademiska Hospital. Uppsala, Sweden References 1 Nordstrom M Increasing incidence of non-Hodgkin's I)mphomas in Swe- den 1958-1992 Oncol Rep 1996.3 645-649 2 Hardell L, Eriksson M. Lenner P. Lundgren E Malignant lymphoma and t immune deficiency increases the risk for NHL."-'' Recently, we presented results from a case-control study on NHL and adipose tissue concentrations of some organochlorine~.".'W~ e chose as controls surgical patients without cancer. We found negligible effects for dioxins, dibenzofurans, dichlorodiphenyldichloroethylene, or hexachlorobenzene. Several of the higher and more persistent polychlorinated biphenyls (PCBs) were elevated in cases, however. The mean concentration of total PCBs was 1,614 ng per gm lipid (range = 637-4,705 ng per gm lipid) in the 27 cases, vs 1,213 ng per gm lipid (range = 366-2,282 ng per gm lipid) in the 17 controls. The sum of chlordanes was 180 ng per gm lipid (range = 48.3-678 ng per gm lipid) in the cases, us 92.8 ng per gm lipid (range = 37.0-164 ng per gm lipid) in the controls. Now we have analyzed the sum of PCBS and chlordang in a multivariate logistic regression analysis controlling for age and sex. The odds ratio (OR) for the sum of PCBs higher than the median concentration of 1,300 ng per gm lipd (taken as exposed) was 1.8 (95% confidence interval (CI) = 0.4-7.41. For the sum of chlordanes higher than the median concentration of 119 ng per gm lipid, we estimated an OR of 3.3 (95% C1 = 0.7-16.2). We found little difference by clinical stage of NHL and between men (N = 17 cases) and women (N = 10 cases). Cases and controls had similar age distributions, and we found no important relation with body mass index. No case or control reported occupational exposure to PCBs or chlordanes, so these findings relate to general population exposure levels. Since both PCBs and chlordanes may cause immunologic impairment in exposed subjec~s,'~oJu~r findings, although based on small numbers, support the hypothesis that agents that are immunotoxic increase the risk for NHL. Lennan liardell Depvtment of Cncolos), h b r o Medical Center, '3-70185 Orebro, Sweden (address correspondence to: Lennart Hardell) -ran Liljegren Department of Surgery, Orebro Medical Center Gunilla Lindstriim Bert van Bavel Depamnent of Environmental Chemistry, Umea Universir).. UmeA. Sweden lymphoproliferative diseases and in patients without a malignant disease. Eur J Cancer Prcv 1995;4:225-229. 5. TOM T. Esser C, Schneider EM, Steinmann-Steiner.Haldenst$tt W, Gleichmann E. Persistence of decreased T-helper cell function in industrial workers 20 years after exposure to 2.3.7.8-tettach~ru-p-~~oxEinnv.uon Health Perspect 1996;104:422-426. 6. Kverliet NI. Brauner JA. Mechanisms of 1.2.3.4.6.7.8-heptachlordi~~~ p-dioxin (HpCDD)-inducedhumoral immune suppression: evidence of primary defect in T-cell regulation (puhlished erratum appears in TOXKAOp~pl Pharmacol 1987;89:148). Toxicol Appl Pharmacol 1987;87:18-31. 7. Exon JH, Koller LD. Effects of chlorinated phenols on immunity in rats. Int J lmmunopharmacol 1985;7:239-247. 8. Daniel V. Huber W, Bauer K, Opelz G. Impaired in-vitro lymphocyte resplnses in patients with elevated pentachlorophenol (PCP) blood levels. Arch Environ Health 1995;50:287-292. 9. S h m a RP. Reddv RV. Toxic effects of chemicals on the immune svstem. In: Haley TJ,ed. Handbook of Toxicology. Washington E:Hemisphere Publishtng, 1987;423-435. 10. Ling. Sung- H, Araki S. Tanigawa T, Sakurai S. Selective decrease of the suppressor-inducer (CW'CG5RA')T lymphocytes in workers exposed to benndmne and beta-naphthylamine. Arch Envirun Health 1995;5@196-199. 1I. Faustini A, Settimi L. Pacifici R. Fano V. Zuccaro P. Forasriere F. Immunological changes among farmers exposed to phenoxy herbicides: preliminary ohservations. Occup Environ Med 1996;53:583-585. 12. Hmver R. Fraumeni JF Jr. Risk of cancer in renal-transplant recipients. Lancet 1973;2:55. 13. Kinlen LJ, Sheil AGR. Peto J. Doll R. Collabrative United KingdomAustralasian study of cancer in patients treated with immunosuppressive drugs. BM] 1979;2:1461-1466. 14. Hardell L, van Bavel B, Lindstrom G. Fredrikson M,Hagberg H. Liljegren G. Nordstrbm M, johansson B. Higher concentrations of specific polychlorinated hiphenyl congeners in adipme tissue from non-Hdgkin's lymphoma patients compared with controls without a malignant disease. Int J Cncol 1996;9:603-608. 15. Hardell L, Liljegren G, Lindstrom G, van Bavel 8. Broman K. Fredrikson M. Hagherg H, Nordstrom M,Johansson 8. lncreased concentrations of chlordam in adipose tissue from non-Hdgkin's lymphoma patients compared with controls without a malignant disease. Int J Oncol 1996;9:1139-1142. 16. Lu YC. Wu YC. Clinical findings and immunological abnormalities in Yu-Cheng patients. Environ Health Petspect 1985;59:17-29. 17. McConnachie PR, Zahalasky AC. Immune alterations in humans e x p o d to the rermiticide technical chlordane. Arch Environ Health 1992;47:295301. Epidemiology and the Internet To the Editor: We read with interest Part I1 of the recent editorial on "Epidemiology and the Internet," related to the use of the World Wide Web (WWW) for conducting prospective cohort studies.' O u r interest arises not only from a shared curiosity regarding the application of new information technologies to