By Sara Amolegbe
The health consequences of chemical exposures in the environment may cost the world more than 10 percent of the global gross domestic product (GDP). According to a new study published in the journal Environmental Health by NIEHS-funded researchers, previous studies may have underestimated these costs by leaving out some less obvious health effects and focusing on only a portion of the contaminants to which people are exposed. This study considered a broader set of exposures such as air pollution, lead, mercury, and pesticides and calculated how much they cost societies in terms of not just clinical illness and death, but also lost wages and productivity.
According to the authors, Philippe Grandjean, M.D., Ph.D., from the Harvard T.H. Chan School of Public Health, and Martine Bellanger, Ph.D., from the EHESP School of Public Health in France, “Our findings suggest that a revised paradigm is required for evaluating and prioritizing the environmental contribution to human illness and the associated costs.”
Rethinking Disease Burden Calculations
The study suggests that calculations in the Lancet Global Burden of Disease study substantially underestimated the economic costs associated with preventable environmental risk factors. The Lancet study found chemical exposures contributed about 5 percent of total global disability adjusted life years (DALYs) lost, a measure that combines degree of lowered quality of life with duration.
“We were surprised that the recent Lancet review concluded that environmental risk factors contribute only 5.18 percent of the total ill health globally,” Grandjean said. “We soon realized that part of the explanation was that the researchers relied only on causal factors that were fully documented and left out many environmental hazards that are fairly well known, such as subclinical lead poisoning.”
For example, the Lancet study examined lead poisoning in terms of defined intellectual disabilities, such as mental retardation, but did not look at more incremental deficits such as reduced brain function and IQ losses, which can also impact human health and influence costs to society. The study’s calculations reflected costs attributed to lead exposure only without including other global neurotoxicants like arsenic. Grandjean’s study states that global arsenic costs may be similar in magnitude to costs associated with lead exposure, but the levels of exposure and response are not as well documented.
“To obtain a better overview, we combined three different approaches to assess the impacts of environmental hazards, an approach that had not been attempted before,” said Grandjean. “While we are still limited by incomplete knowledge on dose-response relationships and distributions of exposures, we obtained a clearer picture of the adverse health impacts caused by environmental hazards.”
Linking Disease Burden to Economic Costs
The new study used assessments of chemical exposures and disease burden not only in terms of DALYs, but also in terms of the economic value of environmentally-related adverse health outcomes. “Valuing health outcomes is a way to reflect the importance people place on their health,” said Bellanger. “This value can be approached by asking people how much they are willing to pay for getting protected from some environmental exposures.”
The researchers included available toxicological and epidemiological information and data on exposure distributions for a range of chemicals that had not been assessed for global burden of impacts before, despite the fact that substantial data were available to determine adverse effects based on level of exposure. Some of the added exposures included neurotoxicants and endocrine disrupting chemicals.
Recognizing Environmental Risk Factors
The study emphasized the importance of including risks that may be considered uncertain as well as any associated subclinical conditions.
“We need to get used to the fact that we will never have complete documentation on all important hazards,” said Grandjean. “There are likely thousands of hazardous chemicals, and we need to protect human health, even if we don't have complete evidence of their effects.”
According to the authors, a major obstacle in assessing risks attributed to environmental chemicals is incomplete documentation of exposure distributions, especially in countries beyond Europe and North America. “We recognize there are limitations to what can be calculated in terms of costs due to the lack of exposure information and incomplete effects data, so our results are likely underestimated,” Bellanger added.
“Based on this approach, we can also see where we need better documentation, especially on exposure levels in industrializing countries,” Grandjean added. This would require more research, which would better inform decisions about the scope of disease and dysfunction associated with environmental chemicals around the world.
Grandjean hopes the study gets into the hands of policymakers to help refocus priorities in protecting people’s health.
Citation: Grandjean P, Bellanger M. 2017. Calculation of the disease burden associated with environmental chemical exposures: application of toxicological information in health economic estimation. Environ Health 16(1):123.