The recent attempt to poison Ukrainian President, Viktor Yuschenko with dioxins, raised public concern regarding this toxic chemical. In industrial countries, there is a constitutive exposure of humans to dioxin compounds, which are formed as by-products in manufacturing processes of various chlorinated organic chemicals and in waste incinerators. Dioxins are extremely stable in the environment and have a low turnover rate in the body--sometimes they are detected years after the original exposure. Of the dioxins, the most notoriously famous is the TCDD (2,3,7,8 tetrachlorodibenzo-p-dioxin). Dioxins exhibit high acute toxicity in various animal species. Humans, however, are considered less susceptible and so far there were no reported deaths following acute dioxin poisoning. Nevertheless, numerous adverse health effects are attributed to dioxin exposure. The most prominent is the chloracne--an acute acneiform eruption, usually appearing on facial skin. There is a solid evidence base that some dioxins are carcinogens. Other long-term deleterious effects of dioxin include: immunosuppression, effects on reproduction, impairments in developmental, neurological and cognitive functions in infants, increased risk for diabetes and cardiovascular diseases and various hormonal alterations. The action of dioxins resembles that of hormones, since their toxicity is mostly receptor-mediated. Dioxins manifest their toxicity in extremely low concentrations. Although there are compounds that exhibit their biological activity at even lower dose range (e.g. nerve gases), this potency of dioxins is considered extraordinary, since there is an every-day exposure to dioxins through environmental vectors mostly via the food chain. Until now, there is no antidotal cure for dioxins, but only symptomatic treatment combined with techniques that accelerate its excretion rate from the body.
The epidemiological data based on the exposure of pentachlorophenol (PCP) and cancer incidence and mortality were analyzed to study the relationship between PCP exposure and cancer risk.
According to the online search of relevant literatures, Poisson regression was used to analyze mortality rates for major cancer sites and fixed-effect model was employed to assess cancer SMR. The dose-response relationship between PCP exposure and cancer risk was also analyzed.
Major cancer mortality rates of exposure populations researched in American and Canadian studies were approximate to or lower than national male cancer mortality rates respectively. The incidence rate of colorectal cancer in occupational exposure population was over 16.4 times in comparison with the population exposed from to drinking water and food. The pooled SMR value of kidney cancer was 1.34 (95% CI 1.02-1.77). The pooled RR for major cancer mortality increased with the rise of PCP exposure level.
A potential dose-response relationship between PCP exposure and cancer risk could exist. In comparison with to the population to exposed from the drinking water and food, the risk of colorectal cancer in occupational exposure population was higher. PCP may be one of the risk factors of the kidney cancer in occupational exposure population.
BACKGROUND: Major congenital malformations are a leading cause of perinatal morbidity and mortality. Congenital malformations are caused by three factors: genetic, environmental or multifactorial, all of which are present in the context of artificial reproductive techniques. FINDINGS: In 1999 Bergh et al. conducted a retrospective study, which included all the children born following IVF treatment in Sweden. The relative risk found was RR = 1.39 [95% CI 1.25-1.54] and there was no stratification for maternal age and parity. In 2002 Hansen et al. conducted a well-established retrospective study in Western Australia. When only term singletons were included in the study, the OR found was OR = 2.1 [1.4-3.2] in the IVF group and OR = 2.2 [1.2-4] in the ICSI group. Results were stratified for maternal age, parity and offspring sex. A meta-analysis of 19 studies found a relative risk of 1.29 for major malformations among IVF pregnancies. DISCUSSION: Explanations for the increased risk of fetal malformations could be divided into three categories: first, the characteristics of the infertile population which include many risk factors: older age, lower parity, chronic diseases and infertility itself. Second, the techniques used to treat infertility are not physiologic. Third, the characteristics of the pregnancy achieved: the incidence of high-order pregnancies is much greater and this fact exposes the offspring to other risk factors such as preterm birth and low birth weight. CONCLUSIONS: Major advances in reproductive techniques offered hope for many couples, but they were also the reason for much concern regarding the outcome of the awaited offspring. The recent studies seem to justify some of those doubts.