"Increased concentrations of polychlorinated biphenyls, hexachlorobenzenes, and chlordanes": response from Hardell and Eriksson.We thank Joffe for his interest in our paper (Hardell et al. 2003). To prevent introducing selection bias, the treating physicians asked all patients to consent to be included in a sequential way, regardless of tumor type, family history, occupation, or place of residence. We included only cases who were patients of physicians involved in the study; therefore, patients of other physicians were not included. In epidemiologic studies, the purpose of controls is to represent the population from which the cases are recruited. In Sweden all patients with testicular cancer testicular cancer Malignant tumour of the testis, or testicle. Although relatively rare, testicular cancer is the most common malignancy for men between the ages of 20 and 34. It typically affects men between 15 and 39 years old. are referred to the university clinics in the national health system regardless of insurance or other factors. Thus, it is highly preferable to use the national population registry for recruiting controls instead of using other hospital patients, who are not representative of the whole population. Joffe is concerned that there is a possible imbalance of agricultural or rural background among cases mad controls. However, the study was balanced in this respect; only 6 cases (10%), 6 controls (10%), 7 case mothers (16%) and 8 control mothers (18%) lived in a rural area. The persistent organochlorines organochlorines see chlorinated hydrocarbons. organochlorines poisoning cause excitement and irritability, tremor, ataxia, weakness, paralysis, convulsions. analyzed in our study (Hardell et al. 2003) were chosen a priori a priori In epistemology, knowledge that is independent of all particular experiences, as opposed to a posteriori (or empirical) knowledge, which derives from experience. because of their likelihood of being present in the food chain in Sweden. Furthermore, as we stated in our article, high concentrations were found in the food chain during the period when the cases and controls in our study were born. Regarding polychlorinated biphenyls polychlorinated biphenyls, (pol´ēklôr´  nā´tid bīfē´n (PCBs), 37 congeners were analyzed, but we reported only the sum of PCBs. It would be interesting to group the studied organochlorines, including the 37 PCB PCB: see polychlorinated biphenyl. PCB in full polychlorinated biphenyl Any of a class of highly stable organic compounds prepared by the reaction of chlorine with biphenyl, a two-ring compound. congeners, according to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. their possible hormonal activity, but at present, animal and human data are insufficient. The authors declare they have no competing financial interests. REFERENCE Hardell L, van Bavel B, Lindstrom G, Carlberg M, Dreifaldt AC, Wijkstrom H, et al. 2003. Increased concentrations of polychlorinated biphenyls, hexachlorabenzene, and chlordanes in mothers of men with testicular cancer. Environ Health Perspect 111:930-934. Lennart Harden Department of Oncology University Hospital Orebro, Sweden E-Mail: lennart.hardell@orebroll.se Mikael Eriksson Mikael Eriksson is a Swedish footballer currently playing for Jönköpings Södra IF in the Swedish Superettan. He has previously played for Degerfors IF. [1] Department of Oncology University Hospital Lund, Sweden |
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