Human cancer from environmental pollutants: the epidemiological evidence

Our plain-English summary of Human cancer from environmental pollutants: the epidemiological evidence, by P. Boffetta (Mutation Research, 2006).

The study

• Author: P. Boffetta
• Journal: Mutation Research
• Published: 2006;608(2):157-62
• Type of article: Review
• Cited by: 123 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

An increased risk of mesothelioma has been reported among individuals experiencing residential exposure to asbestos, while results for lung cancer are less consistent. Several studies have reported an increased risk of lung cancer risk from outdoor air pollution: on the basis of the results of the largest study, the proportion of lung cancers attributable to urban air pollution in Europe can be as high as 10.7%. A causal association has been established between second-hand tobacco smoking and lung cancer, which may be responsible for 1.6% of lung cancers. Radon is another carcinogen present in indoor air, which may be responsible for 4.5% of lung cancers. An increased risk of bladder might be due to water chlorination by-products. The available evidence on cancer risk following exposure to other environmental pollutants, including, pesticides, dioxins and electro-magnetic fields, is inconclusive.

In plain English

This article reviewed epidemiological evidence linking environmental pollutants to cancer. Using meta-analyses, pooled analyses and selected studies, it estimated attributable cancer cases in the European Union for 2002. For residential asbestos exposure, mainly from outdoor pollution near asbestos mining or manufacturing, a cited meta-analysis estimated relative risks of 3.5 (95% CI 1.8–7.0) for mesothelioma and 1.1 (95% CI 0.9–1.5) for lung cancer. A WHO model put residential exposure at 5% of Europeans, but the author assumed about 2% had exposure comparable to the highly exposed populations studied, estimating 338 mesothelioma cases a year in men and 43 in women. No lung cancer estimate was made because the meta-analysis found no statistically significant increase. The author noted that exposure levels are generally low and that duration and fibre type are seldom known precisely. Other estimates attributed 10.7% of lung cancers to outdoor air pollution (flagged for caution), 1.6% to second-hand smoke and 4.5% to indoor radon. Human evidence on pesticides, dioxins and electromagnetic fields was described as unconvincing or inconclusive. The author advised great caution in interpreting all the estimates.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Review of epidemiological evidence (drawing on published meta-analyses, pooled analyses and selected studies), with estimates of attributable cancer cases
• Who was studied: Published epidemiological studies of environmental pollutants and cancer; burden estimates made for the European Union, 2002
• Exposure: Non-occupational (household and residential) asbestos exposure, mainly outdoor pollution from asbestos mining or manufacturing plus natural erosion of asbestos or asbestiform rocks. Also reviewed: outdoor air pollution, second-hand tobacco smoke, indoor radon, other indoor air pollution, arsenic and chlorination by-products in drinking water, pesticides, dioxins and electromagnetic fields
• Main results:
  • A cited meta-analysis estimated the relative risk of mesothelioma from residential asbestos exposure at 3.5 (95% CI 1.8–7.0)
  • In the same meta-analysis, the relative risk of lung cancer from residential asbestos exposure was 1.1 (95% CI 0.9–1.5)
  • According to a WHO model, 5% of the European population experience residential exposure to asbestos
  • Because the meta-analysis studies involved highly exposed populations, the author used an estimate of about 2% for exposure to comparable circumstances. On that basis the author estimated 338 mesothelioma cases per year in men and 43 in women in the European Union
  • No estimate of asbestos-related lung cancer cases was made because the meta-analysis showed no statistically significant increase
  • Outdoor air pollution: an estimated 10.7% of lung cancers, about 20,942 cases per year in men and 6112 in women (flagged by the author for cautious interpretation)
  • Second-hand smoke from spouses and workplaces: estimated to account for 1.6% of all lung cancers
  • Indoor radon: estimated attributable fraction of lung cancer of 4.5%
  • Pesticides: studies in humans had not provided convincing evidence of increased cancer risk
  • Dioxins: no clear excess of cancer had been shown among heavily exposed populations
  • Electromagnetic fields: no conclusive evidence of a causal association with cancer, so no cases were attributed
• The authors' conclusion: The author concluded that in Europe outdoor air contaminants and indoor radon are the two most important causes of pollution-related cancer, and that the attributable-case estimates call for great caution in interpretation
• Limitations the authors state:
  • Residential asbestos exposure is hard to assess because levels are generally low
  • The duration and frequency of residential asbestos exposure and the fibre type are seldom known precisely
  • The studies in the asbestos meta-analysis were conducted in highly exposed populations. For that reason the author applied the risk estimate to about 2% of Europeans exposed to comparable circumstances, rather than to the 5% with any residential exposure
  • A small increased cancer risk from household asbestos exposure is plausible, but no adequate data exist to quantify it
  • The outdoor air pollution estimate rests on a single study whose relevance to Europe is unclear
  • Uncertainties in risk estimates, exposure prevalence and confounding call for great caution in interpreting all the estimates

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma, Lung Cancer.

Related studies

• Contribution of environmental factors to cancer risk — P. Boffetta, F. Nyberg (2003)
• Environmental health of children — A.M. Dunn, C. Burns, et al. (2003)
• Environmental factors in causing human cancers: emphasis on tumorigenesis — U.T. Sankpal, H. Pius, et al. (2012)
• Unusually high incidence of malignant pleural mesothelioma in a town of eastern Sicily: an epidemiological and environmental study — L. Paoletti, D. Batisti, et al. (2000)
• What every physician should know about environmental health — C. Carlsten, J. Croke (1997)
• Adverse health effects of fluoro-edenitic fibers: epidemiological evidence and public health priorities — C. Bruno, P. Comba, et al. (2006)

Browse more research in Mutation Research, or return to medical research.