Exposure to environmental chemicals and heavy metals, and risk of pancreatic cancer

Our plain-English summary of Exposure to environmental chemicals and heavy metals, and risk of pancreatic cancer, by S.O. Antwi, E.C. Eckert, C.V. Sabaque, et al (Cancer Causes & Control, 2015).

The study

• Authors: S.O. Antwi, E.C. Eckert, C.V. Sabaque, E.R. Leof, K.M. Hawthorne, W.R. Bamlet, K.G. Chaffee, A.L. Oberg, G.M. Petersen
• Journal: Cancer Causes & Control
• Published: 2015;26(11):1583-91
• Cited by: 76 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Purpose: Exposure to various chemicals and heavy metals has been associated with risk of different cancers; however, data on whether such exposures may increase the risk of pancreatic cancer (PC) are very limited and inconclusive. We examined PC risk with self-reported exposures to chemicals and heavy metals.

Methods: The design was a clinic-based, case-control study of data collected from 2000 to 2014 at Mayo Clinic in Rochester, Minnesota, USA. Cases were rapidly ascertained patients diagnosed with pancreatic ductal adenocarcinoma (n = 2,092). Controls were cancer-free patients in primary care clinics (n = 2,353), frequency-matched to cases on age, race, sex, and state/region of residence. Cases and controls completed identical risk factor questionnaires, which included yes/no questions about regular exposure to pesticides, asbestos, benzene, chlorinated hydrocarbons, chromium, and nickel. Unconditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CI) comparing those who affirmed exposure to each of the chemicals/heavy metals to those who reported no regular exposure, adjusting for potential confounders.

Results: Self-reported regular exposure to pesticides was associated with increased odds of PC (OR 1.21, 95% CI 1.02-1.44). Regular exposure to asbestos (OR 1.54, 95% CI 1.23-1.92), benzene (OR 1.70, 95% CI 1.23-2.35), and chlorinated hydrocarbons (OR 1.63, 95% CI 1.32-2.02) also was associated with higher odds of PC. Chromium and nickel exposures were not significantly associated with PC.

Conclusions: These findings add to the limited data suggesting that exposure to pesticides, asbestos, benzene, and chlorinated hydrocarbons may increase PC risk. They further support the importance of implementing strategies that reduce exposure to these substances.

In plain English

This case-control study at Mayo Clinic in Rochester, Minnesota, compared 1,892 patients with pancreatic ductal adenocarcinoma (a type of pancreatic cancer) against 2,316 cancer-free primary care patients. Participants answered yes or no to whether they were ever regularly exposed to asbestos, pesticides, benzene, chlorinated hydrocarbons, chromium and nickel. The questions covered work and non-work exposure. The article did not name asbestos fiber types. Regular asbestos exposure was reported by 240 cases and 178 controls. After adjusting for age, sex, smoking, diabetes, body mass index and education, asbestos exposure was associated with higher odds of pancreatic cancer (OR 1.54, 95% CI 1.23–1.92). Pesticides, benzene and chlorinated hydrocarbons were also associated with higher odds. The associations for chromium and nickel were not statistically significant. The authors concluded that the findings lend support for a role of environmental chemicals and heavy metals in pancreatic cancer. They noted several limitations: possible recall bias, clinic-based participants, exclusion of people with missing data, and no detailed job data.

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: Clinic-based case-control study
• Who was studied: Patients at Mayo Clinic, Rochester, Minnesota, USA. Cases had histologically confirmed pancreatic ductal adenocarcinoma and were evaluated between 6 October 2000 and 29 December 2014. Controls were cancer-free Mayo Clinic primary care patients recruited between 25 May 2004 and 20 March 2012, frequency-matched to cases on age, race, sex and region of residence. 2,092 cases and 2,353 controls completed questionnaires; 1,892 cases and 2,316 controls were analyzed. About 98% were of European descent.
• Exposure: Self-reported regular exposure, answered yes or no, to asbestos, chlorinated hydrocarbons, chromium, nickel, insecticides/pesticides and benzene. The questions were meant to capture both work-related and non-work-related exposure. No fiber types, doses or durations were recorded.
• Main results:
  • Asbestos: 240 cases and 178 controls reported regular exposure. The age-adjusted OR was 1.75 (95% CI 1.42–2.14) and the multivariable-adjusted OR was 1.54 (95% CI 1.23–1.92).
  • Pesticides: regular exposure was associated with 21% increased odds of pancreatic cancer (multivariable-adjusted OR 1.21, 95% CI 1.02–1.44).
  • Benzene: multivariable-adjusted OR 1.70 (95% CI 1.23–2.35).
  • Chlorinated hydrocarbons: multivariable-adjusted OR 1.63 (95% CI 1.32–2.02).
  • Chromium and nickel: the associations were suggestive but not statistically significant (OR 1.42, 95% CI 0.89–2.26 for chromium; OR 1.55, 95% CI 0.95–2.52 for nickel).
  • Asbestos by usual work setting (multivariable-adjusted): indoor workers OR 1.55 (95% CI 1.16–2.06); outdoor workers OR 1.15 (95% CI 0.62–2.15); those spending about equal time indoors and outdoors OR 1.83 (95% CI 1.17–2.86). The interaction p value was 0.54.
  • Usual working environment (indoor versus outdoor) was not associated with pancreatic cancer.
  • The pesticide association was confined to people who usually worked indoors (OR 1.48, 95% CI 1.17–1.89; p for interaction 0.01).
  • A sensitivity analysis gave similar conclusions. Imputing 'no exposure' for missing answers produced attenuated odds ratio estimates.
• The authors' conclusion: The authors concluded that the findings lend support for a role of environmental chemicals and heavy metals in the development of pancreatic cancer, and support the need for strategies to reduce exposure to these substances.
• Limitations the authors state:
  • Recall bias, which is inherent to case-control studies.
  • Because cases and controls came from a clinic, the findings may not apply to the broader population.
  • Possible selection bias from excluding 234 participants with missing exposure data.
  • The questionnaire did not explain exposures such as chlorinated hydrocarbons in lay terms.
  • Imputing 'no exposure' for missing answers from 364 participants may have made the odds ratio estimates more conservative.
  • Detailed occupational exposure analysis was not possible because job titles, job functions and durations were not available.

Topics

Medical terms in this study, explained in our Lexicon: Case-Control Study, Adenocarcinoma, Odds Ratio, confidence interval.

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