Carcinogens retrospective

Several retrospective cohort studies of workers exposed to unquantified levels of trichloroethylene have been conducted. All of these studies have limitations that restrict their usefulness for evaluating the carcinogenicity of trichloroethylene. None has shown clear, unequivocal, evidence that trichloroethylene exposure is linked to increased cancer risk. 

No information on the carcinogenic potential of polyalphaolefin hydraulic fluids was located. Studies designed to assess carcinogenicity in animals exposed via inhalation, oral, and dermal routes or a well-controlled cohort retrospective or prospective study would be useful for determining the carcinogenic potential of polyalphaolefin hydraulic fluids. 

In order to establish a causal relationship rather than a pure association between the suspected carcinogen Rn-d and the induced effect lung cancer it is most important to know the individual Rn-d exposure. This is the particular weakness of all these studies since these measurements were not carried out fifteen to thirty years ago, this essential information cannot be provided by any of the available retrospective studies with a sufficient degree of reliability and accuracy (Steinhausler, in press). Therefore they have to rely on indirect estimation of past Rn-d exposure levels, using e.g. inference from uranium ore content. 

Lewis, D. F., Iannides, C., and Parke, D. V. (1995) A retrospective evaluation of COMPACT predictions of the outcome of NTP rodent carcinogenicity testing. 

Retrospective identification of risk from waterborne infectious disease is a relatively simpler task compared with carcinogenic risks. Many acute effects can be identified with proper population surveillance, related to probable origin, and quantified. Assessments of microbial risks from theoretical projections would be extremely complex. They... 

BaiUn PL, Tindall JP, Roenigk HH Jr, Hogan MD. Is methotrexate therapy for psoriasis carcinogenic A modified retrospective-prospective analysis. JAMA 1975 232(4) 359-62. 

Cancer. Carcinogenicity of PCBs in humans has been investigated in retrospective occupational studies that evaluated cancer mortality in workers exposed during capacitor manufacturing and repairing, and in case-control studies of the general population that examined associations between cancer and serum or adipose tissue levels of PCBs resulting from environmental exposures. Based on indications of... 

Even if there were no such limitations, epidemiologic analysis is retrospective study it cannot be depended upon for the detection and prevention of potential health hazards to the public. In comparison to epidemiologic studies, animal bioassays are short in duration, relatively inexpensive, easily perfomed under controlled conditions, and are reliable predictors for known human carcinogens. Therefore, from the point of view of identifying and preventing public health hazards, animal bioassay is an invaluable tool. 

Case-control and retrospective cohort studies have been very successful in identifying large scale determinants of cancer such as smoking which may be responsible for as much as 30% of all cancers in developed countries. These types of studies also have been successful in identifying several occupational carcinogens such as 2-napthylamine, asbestos, and vinyl chloride. Although only small numbers of individuals were exposed in these occupational cases it... 

Effect. The urinary bladder is a target organ for MBOCA-induced carcinogenicity (Ward et al. 1990). Retrospective biological monitoring using cystoscopy would help identify new biomarkets necessary to characterize the preneoplastic state of the urinary bladder. 

As with all carcinogens the carcinogenic potency of solvents has been assessed by short-term in vitro tests, e. g., Ames assay, by long-term tumor induction experiments in animals and - especially important for the evaluation of the carcinogenic action in humans -prospective and retrospective epidemiological studies, for solvent exposure mainly in work places. 

Several retrospective cohort studies have shown a significant correlation between chronic consumption of ethanol and the development of hepatocellular carcinoma. In this review, several mechanisms by which ethanol could exert its effects have been considered. Ethanol itself does not appear to be carcinogenic or genotoxic, but it may modify either the ini-... 

Retrospective mortality studies99 in 2,567 workers (> 3 months employment) from two capacitor manufacturing plants showed that mortality in both plants was lover than expected and there were no significant increases in either liver or rectal cancer. A study on 31 workers exposed to Aroclor 1254 and other chemicals vtiile employed in a New Jersey petrochemical plant 100 showed an increased incidence of malignant melanomas (0.04% expected 0.13% observed) however, due to the small populations involved in this survey, more comprehensive long term epidemiologic studies will be required to fully assess the carcinogenicity of PCBs. Hovever, it is apparent from most reports that occupational exposure to PCBs results in characteristic toxic symptoms vhich appear to be reversible. 

Future studies on the adverse human health effects of PCBs will require more standardized methods of congener specific PCB analysis, the development of more sensitive techniques to determine subtle toxic effects caused by relatively low exposures to PCBs (e.g. environmental) and a more thorough knowledge of the interactive effects of PCBs with other environmental pollutants. The most appropriate indicators of the adverse health effects of PCBs and their role in carcinogenicity will be determined from the continuing epidemiological and retrospective studies on occipationally exposed workers. 

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