Designer epidemiology

Deseriptive data are available from reports of humans exposed to 1,4-diehlorobenzene by inhalation (and possibly dermal contact). It is important to note that the case studies discussed in this section should be interpreted with caution since they reflect incidents in which individuals have reportedly been exposed to 1,4-dichlorobenzene, and they assume that there has been no other exposure to potentially toxic or infectious agents. There is usually little or no verification of these assumptions. Case studies in general are not scientifically equivalent to carefiilly designed epidemiological studies or to adequately controlled and monitored laboratory experiments. Thus, the case studies described below should be considered only as providing supplementary evidence that 1,4-dichlorobenzene may cause the reported effects. 

Kanitz et al. 1996 Tuthill et al. 1982). However, these studies had limitations in their designs that affect their interpretability. Well-designed epidemiological studies of populations orally exposed to chlorine dioxide in the drinking water could provide valuable information regarding safe levels. 

Wacholder S (1991) Practical considerations in choosing between the case-cohort and nested case-control designs. Epidemiology, 2 155-158. 

Evaluation of TVOC and SBS/health effects from carefully designed epidemiological studies. 

The committee concludes that there do not appear to be any serious flaws in the design and conduct of the Seychelles, Faroe Islands, and New Zealand studies that would preclude their use in a risk assessment. However, because there is a large body of scientific evidence showing adverse neurodevelopmental effects, including well-designed epidemiological studies, the committee concludes that an RfD should not be derived from a study, such as the Seychelles study, that did not observe any associations with MeHg. 

The New Zealand, Faroe Islands, and Seychelles studies are well-designed epidemiological investigations in which prenatal MeHg exposures were within the range of at least some U.S. population exposures. Any revision of the RfD or other exposure standards should consider the findings of these studies. 

Overview of Basic Epidemiologic Study Designs. Epidemiology is the systematic study of the distribution and determinants of disease in human populations (19). Analytic research studies fall into several designs such as cohort studies, case-control studies, proportional mortality ratio (PMR) studies and cross sectional studies. The choice of a particular study design is determined by the... 

Despite the power of well-designed epidemiological studies to detect differences in disease frequencies in human populations, it is important to keep in mind that statistical significance is not the same as toxicological significance. To make a convincing connection between chemical exposure and disease, one or more additional kinds of evidence are needed. First, there must be evidence that the at-risk population was actually exposed to the chemical of concern. Second, the chemical should obey the dose-effect relationship, i.e., the incidence of the toxic effect of concern should, if possible, be shown to increase as a function of exposure, either in the... 

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