ISSN:1176-2551    

出版商:ADIS    

年代:2003

数据来源: ADIS

ISSN:1176-2551    

出版商:ADIS    

年代:2003

数据来源: ADIS

摘要:

Despite the enormous number of reports on polychlorinated biphenyl (PCB) toxicology, both the causal interpretation of epidemiological studies and the risk assessment of human exposures have been hampered by the lack of information on the pharmacokinetics of various PCB isomers and congeners. Thus, the assessment of exposure by means of measuring either total PCBs or individual congeners in the blood has so far been unsatisfactory. For example, the concentration and the pattern of congeners in the blood did not correlate with that at site(s) of action. In fact, the same levels of blood PCBs correlated with either toxic effects or no effects (both in clinical and epidemiological studies). In addition, when toxicity caused by PCBs was observed, the severity of the signs did not correlate with blood levels.Reasons for such a qualified failure are manifold and include different ways of reporting blood measurements, the different toxicological characteristics of each PCB, and different timing of sampling the blood, etc. Therefore, only limited conclusions can be drawn concerning what blood PCB measurements mean.

ISSN:1176-2551    

出版商:ADIS    

年代:2003

数据来源: ADIS

摘要:

Polychlorinated biphenyls (PCBs) are a mixture of chemicals. Some congeners of the mixture are highly persistent both in the environment and in humans. Although PCBs have not been used commercially since about 1977 in the US, they can still be detected in human blood and tissues in this country. PCB levels are declining and are often no longer detectable in younger people. A cursory review of recent animal studies is provided. Studies to determine whether PCBs cause cancer in humans, neurobehavioural effects, abnormal thyroid and immune function in children and low birth weight are discussed in more detail. These studies are inconclusive and do not provide clinical evidence that PCBs at levels encountered with human exposure produce adverse health effects. The differences in PCB blood or tissue concentrations between controls and cases, or between the upper and lower end of various environmentally exposed groups of children or adults, are small. Although some effects are statistically significantly different, they do not appear to be biologically significant. Many studies on the effects of PCBs are difficult to interpret because the range of normal values for clinical and neurobehavioural tests are not provided or appropriately considered, there was no, or inadequate, control for potential confounders. In occupational mortality studies, exposures were much higher. In some studies, various specific cancers were elevated. However, these appear to be chance observations resulting from multiple comparisons since the increase of specific cancers was not consistent between studies and was no longer present in some cohorts when studies were repeated at a later date with longer follow-up. Overall, the data fail to demonstrate conclusive adverse health effects of PCBs at concentrations encountered with human exposures.

ISSN:1176-2551    

出版商:ADIS    

年代:2003

数据来源: ADIS

摘要:

Idiopathic environmental intolerance (IEI) is a descriptor for a phenomenon that has many names including environmental illness, multiple chemical sensitivity and chemical intolerance. Toxicogenic and psychogenic theories have been proposed to explain IEI. This paper presents a causality analysis of the toxicogenic theory using Bradford Hill's nine criteria (strength, consistency, specificity, temporality, biological gradient, biological plausibility, coherence, experimental intervention and analogy) and an additional criteria (reversibility) and reviews critically the scientific literature on the topic. The results of this analysis indicate that the toxicogenic theory fails all of these criteria. There is no convincing evidence to support the fundamental postulate that IEI has a toxic aetiology; the hypothesised biological processes and mechanisms are implausible.

ISSN:1176-2551    

出版商:ADIS    

年代:2003

数据来源: ADIS

摘要:

Toxicogenic and psychogenic theories have been proposed to explain idiopathic environmental intolerance (IEI). Part 2 of this article is an evidence-based causality analysis of the psychogenic theory using an extended version of Bradford Hill's criteria. The psychogenic theory meets all of the criteria directly or indirectly and is characterised by a progressive research programme including double-blind, placebo-controlled provocation challenge studies. We conclude that IEI is a belief characterised by an overvalued idea of toxic attribution of symptoms and disability, fulfilling criteria for a somatoform disorder and a functional somatic syndrome. A neurobiological diathesis similar to anxiety, specifically panic disorder, is a neurobiologically plausible mechanism to explain triggered reactions to ambient doses of environmental agents, real or perceived. In addition, there is a cognitively mediated fear response mechanism characterised by vigilance for perceived exposures and bodily sensations that are subsequently amplified in the process of learned sensitivity. Implications for the assessment and treatment of patients are presented.

ISSN:1176-2551    

出版商:ADIS    

年代:2003

数据来源: ADIS