Evaluation of the health effects of cadmium : application of the systematic review
(2005)
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- Abstract
- Background: Several health hazards have been associated with cadmium exposure. In workers, mainly exposed by inhalation to cadmium compounds, toxic effects affecting the lung, kidney and skeleton have been reported. For the general population primarily exposed through the diet, main target organs are the kidney and the bone. Results from experimental and epidemiological studies have also suggested that cadmium may be genotoxic and carcinogenic. For some of these effects, the huge amount of literature available on cadmium did not allow to elucidate definitely outcomes associated with cadmium exposure or their mechanisms. As exposure to cadmium and its compounds still exists and as it cumulates in the human body over the years, a thorough evaluation of the health risk associated with cadmium exposure is required in order to identify if and where risk reduction strategies should be applied. Objective: The main objective of the work was to address three pending issues of public health relevance. Aim was to focus on the remaining uncertainties about effects of most concern, expected to occur upon repeated, long-term exposure to cadmium. Research questions are summarised as follows: What is the evidence that cadmium exerts genotoxic effects in humans? What is the evidence that cadmium is a carcinogen in humans? What is the evidence that cadmium is a cause of clinically relevant chronic renal disease? To address these questions, we have reviewed and synthesised the existing literature using the principles and methods of the systematic review, which we consider to be an interesting tool in the risk assessment of chemicals. After applying principles and methodology of the systematic review to the three reseach questions, interests and limitations of the systematic review were discussed. Results: Regarding genotoxic and carcinogenic effects associated with cadmium exposure, reviewing systematically the available data allowed to identify the sources of diversity across the various types of studies and to detect deficiencies in the design, conduction, analysis and interpretation of research. With regard to the long-term course of cadmium-associated kidney effects, no strong evidence supporting a causal role of cadmium could be drawn from the systematic review of the data, except when exposure had been very high. Cadmium rather than being a primary cause for clinical kidney disease might also contribute to accelerate the progress of concurrent renal diseases such as diabetes. Conclusions: Overall, systematic reviews presented several benefits for the evaluation of the health risks of cadmium. They reviewed and summarised the existing evidence on a topic, allowed to compare exposure assessments carried out in different studies. They enabled a gain in clarity and in awareness with respect to the evidence that was available or not. They obliged to better identify and recognise the uncertainties remaining in our knowledge and emphasise their sources. Systematic reviews are valuable instruments in resolving inconsistencies between primary studies and in identifying some of the causes of discrepancies. They present, however, several limitations: first of all, the quality of the systematic reviews depends on the quality of the primary studies available. A second limitation is that systematic reviews are actively interpreted syntheses, not exempt from some subjectivity. Reviewers have to make value-laden judgements on for instance how to phrase research questions, which inclusion criteria to apply what data to extract. There is also a danger that confidence in the systematic review recipe may lead people into a false sense of security about the lack of bias in the conclusions drawn.
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Verougstraete, V. (2005). Evaluation of the health effects of cadmium : application of the systematic review. https://hdl.handle.net/2078.5/110693