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. 2021 Nov 15;9(11):308.
doi: 10.3390/toxics9110308.

Human Chemical Exposure from Background Emissions in the United States and the Implication for Quantifying Risks from Marginal Emission Increase

Dingsheng Li  1 , Li Li  1
Affiliations

Human Chemical Exposure from Background Emissions in the United States and the Implication for Quantifying Risks from Marginal Emission Increase

Dingsheng Li et al. Toxics. .

Abstract

The linear dose-response relationship has long been assumed in assessments of health risk from an incremental chemical emission relative to background emissions. In this study, we systematically examine the relevancy of such an assumption with real-world data. We used the reported emission data, as background emissions, from the 2017 U.S. National Emission Inventory for 95 organic chemicals to estimate the central tendencies of exposures of the general U.S. population. Previously published nonlinear dose-response relationships for chemicals were used to estimate health risk from exposure. We also explored and identified four intervals of exposure in which the nonlinear dose-response relationship may be linearly approximated with fixed slopes. Predicted rates of exposure to these 95 chemicals are all within the lowest of the four intervals and associated with low health risk. The health risk may be overestimated if a slope on the dose-response relationship extrapolated from toxicological assays based on high response rates is used for a marginal increase in emission not substantially higher than background emissions. To improve the confidence of human health risk estimates for chemicals, future efforts should focus on deriving a more accurate dose-response relationship at lower response rates and interface it with exposure assessments.

Keywords: background emission; dose–response relationship; exposure modeling; human health risk assessment.

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Conflict of interest statement

The authors declare no conflict of interest. No third-party funders had a role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
Schematic overview of the modeling approach in this study.
Figure 2
Figure 2
Average daily doses (ingestion in blue and inhalation in orange) of 95 organic chemicals for 3-, 14-, and 25-year-old individuals predicted in this study based on background emission rates from NEI, ranked by the average daily oral dose for age 3.
Figure 3
Figure 3
The ratio of the average daily dose to ED50 for 95 organic chemicals (ingestion in blue and inhalation in orange) for 3-, 14-, and 25-year-olds predicted in this study based on background emission rates from NEI; the chemicals are ranked in the same order as in Figure 2.
Figure 4
Figure 4
Nonlinear dose–response curve (solid line), approximated linear slopes for four intervals (dashed lines), and extrapolated slope based on ED10 (dotted line). Circles are starting/end points for the intervals.
See this image and copyright information in PMC

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