Structured expert judgement approach of the health impact of various chemicals and classes of chemicals

Our plain-English summary of Structured expert judgement approach of the health impact of various chemicals and classes of chemicals, by D. Marti, D. Hanrahan, E. Sanchez-Triana, et al (PloS One, 2024).

The study

• Authors: D. Marti, D. Hanrahan, E. Sanchez-Triana, M. Wells, L. Corra, H. Hu, P.N. Breysse, A. Laborde, J. Caravanos, R. Bertollini, K. Porterfield, R. Fuller
• Journal: PloS One
• Published: 2024;19(6):e0298504
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Introduction: Chemical contamination and pollution are an ongoing threat to human health and the environment. The concern over the consequences of chemical exposures at the global level continues to grow. Because resources are constrained, there is a need to prioritize interventions focused on the greatest health impact. Data, especially related to chemical exposures, are rarely available for most substances of concern, and alternate methods to evaluate their impact are needed.

Structured Expert Judgment (sej) Process: A Structured Expert Judgment (Research Outreach, 2021) process was performed to provide plausible estimates of health impacts for 16 commonly found pollutants: asbestos, arsenic, benzene, chromium, cadmium, dioxins, fluoride, highly hazardous pesticides (HHPs), lead, mercury, polycyclic-aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), Per- and Polyfluorinated Substances (PFAs), phthalates, endocrine disrupting chemicals (EDCs), and brominated flame retardants (BRFs). This process, undertaken by sector experts, weighed individual estimations of the probable global health scale health impacts of each pollutant using objective estimates of the expert opinions' statistical accuracy and informativeness.

Main Findings: The foremost substances, in terms of mean projected annual total deaths, were lead, asbestos, arsenic, and HHPs. Lead surpasses the others by a large margin, with an estimated median value of 1.7 million deaths annually. The three other substances averaged between 136,000 and 274,000 deaths per year. Of the 12 other chemicals evaluated, none reached an estimated annual death count exceeding 100,000. These findings underscore the importance of prioritizing available resources on reducing and remediating the impacts of these key pollutants.

Range Of Health Impacts: Based on the evidence available, experts concluded some of the more notorious chemical pollutants, such as PCBs and dioxin, do not result in high levels of human health impact from a global scale perspective. However, the chemical toxicity of some compounds released in recent decades, such as Endocrine Disrupters and PFAs, cannot be ignored, even if current impacts are limited. Moreover, the impact of some chemicals may be disproportionately large in some geographic areas. Continued research and monitoring are essential; and a preventative approach is needed for chemicals.

Future Directions: These results, and potential similar analyses of other chemicals, are provided as inputs to ongoing discussions about priority setting for global chemicals and pollution management. Furthermore, we suggest that this SEJ process be repeated periodically as new information becomes available.

Copyright: © 2024 Marti et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

In plain English

This study used structured expert judgement to estimate the worldwide health impact of 16 chemicals and chemical classes, including asbestos. Nine experts, who are also the article's authors, answered 17 calibration questions with known answers, and their accuracy set how much weight each expert's estimates received. They then estimated premature deaths and disability-adjusted life years (DALYs) lost in 2019 from each chemical. For asbestos, the article does not name fiber types or specific asbestos-related diseases. For asbestos, the performance-weighted median estimate was 274,000 premature deaths a year, with a 5th to 95th percentile range of 48,200 to 346,000, and 4,230,000 DALYs lost. Experts estimated that 57% of asbestos deaths occurred in high-income countries and 43% in low- and middle-income countries, and they noted that exposure data in low- and middle-income countries were inadequate. Lead had the highest estimate, at 1,660,000 deaths. The authors concluded that the most hazardous substances were traditional ones: lead, asbestos and arsenic, along with highly hazardous pesticides. They cautioned that the results apply only at a macro level and that many uncertainties persist.

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: Structured expert judgement (expert elicitation). Each expert's estimates were weighted by that expert's performance on calibration questions.
• Who was studied: Nine invited experts, who are included as authors of the article. They gave estimates of global health impacts for 16 chemicals or chemical classes for the year 2019. Each expert first answered 17 calibration questions.
• Exposure: Asbestos, described only generically with no fiber types named, was one of 16 chemicals or classes. The others were arsenic, benzene, chromium, cadmium, dioxins, fluoride, highly hazardous pesticides, lead, mercury, PAHs, PCBs, PFAs, phthalates, endocrine disrupting chemicals and brominated flame retardants. Experts estimated premature deaths and DALYs lost in 2019 from each.
• Main results:
  • Asbestos, performance-weighted estimates of premature deaths per year: 5th percentile 48,200; 50th percentile 274,000; 95th percentile 346,000.
  • Asbestos was estimated to cause 4,230,000 DALYs lost per year.
  • Of asbestos deaths, experts estimated 57% occurred in high-income countries and 43% in low- and middle-income countries.
  • 43% of experts agreed that the science on asbestos dose-response was adequate, and 50% agreed that the science on asbestos exposure levels was adequate.
  • Experts noted inadequate data on asbestos exposures in low- and middle-income countries, so the burden there could be greater than current statistics indicate.
  • The four substances with the highest estimated annual deaths were lead, asbestos, arsenic and highly hazardous pesticides.
  • Lead had the highest estimate: 50th percentile of 1,660,000 premature deaths per year, with a 5th to 95th percentile range of 945 to 3,230,000.
• The authors' conclusion: The authors concluded that the most hazardous substances were traditional ones: lead, asbestos and arsenic, along with highly hazardous pesticides. In their view, old but well-known risks are still the largest.
• Limitations the authors state:
  • The study is meant as a prioritization tool only at a macro (global) level. Its findings may not match the concerns of specific localities.
  • Exposures are not equally distributed. Some communities may have high exposures even where global estimates are modest, for example asbestos in countries still mining or using it.
  • The prominence of lead, asbestos, arsenic and highly hazardous pesticides may partly reflect the experts' familiarity with their hazards.
  • Many uncertainties persist despite the panel's efforts.

Related studies

• Environmental health of children — A.M. Dunn, C. Burns, et al. (2003)
• Human cancer from environmental pollutants: the epidemiological evidence — P. Boffetta (2006)
• Factors that impact susceptibility to fiber-induced health effects — J.E. Below, N.J. Cox, et al. (2011)
• Linking expert judgement and trends in occupational exposure into a job-exposure matrix for historical exposure to asbestos in the Netherlands — P. Swuste, M. Dahhan, et al. (2008)
• High levels of dioxin-like PCBs found in organic-farmed eggs caused by coating materials of asbestos-cement fiber plates: A case study — J. Winkler (2015)
• What every physician should know about environmental health — C. Carlsten, J. Croke (1997)

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