Risk Analysis, Vol. 38, No. 6, 2018 DOI: 10.1111/risa.12933
Characterizing Risk for Cumulative Risk Assessments
Margaret M. MacDonell,
Richard C. Hertzberg,
Glenn E. Rice,
J. Michael Wright,
and Linda K. Teuschler
In assessing environmental health risks, the risk characterization step synthesizes informa-
tion gathered in evaluating exposures to stressors together with dose–response relationships,
characteristics of the exposed population, and external environmental conditions. This arti-
cle summarizes key steps of a cumulative risk assessment (CRA) followed by a discussion
of considerations for characterizing cumulative risks. Cumulative risk characterizations dif-
fer considerably from single chemical- or single source-based risk characterization. CRAs
typically focus on a speciﬁc population instead of a pollutant or pollutant source and should
include an evaluation of all relevant sources contributing to the exposures in the population
and other factors that inﬂuence dose–response relationships. Second, CRAs may include in-
ﬂuential environmental and population-speciﬁc conditions, involving multiple chemical and
nonchemical stressors. Third, a CRA could examine multiple health effects, reﬂecting joint
toxicity and the potential for toxicological interactions. Fourth, the complexities often ne-
cessitate simplifying methods, including judgment-based and semi-quantitative indices that
collapse disparate data into numerical scores. Fifth, because of the higher dimensionality
and potentially large number of interactions, information needed to quantify risk is typically
incomplete, necessitating an uncertainty analysis. Three approaches that could be used for
characterizing risks in a CRA are presented: the multiroute hazard index, stressor grouping
by exposure and toxicity, and indices for screening multiple factors and conditions. Other key
roles of the risk characterization in CRAs are also described, mainly the translational aspect
of including a characterization summary for lay readers (in addition to the technical analysis),
and placing the results in the context of the likely risk-based decisions.
KEY WORDS: Cumulative risk assessment; multiple stressors; risk characterization
Environmental health risk assessments have
usually been comprised of four sequential and
Environmental Science Division, Argonne National Laboratory,
Argonne, IL, USA.
Biomathematics Consulting and Department of Environmental
Health, Emory University, Atlanta, GA, USA.
National Center for Environmental Assessment, Ofﬁce of
Research and Development, U.S. Environmental Protection
Agency, Cincinnati, OH, USA.
Linda Teuschler and Associates, St. Petersburg, FL, USA.
Address correspondence to Richard Hertzberg, Biomathematics
Consulting and Department of Environmental Health, Emory
University, Atlanta, GA 30322, USA; tel: +1-404-291-0087;
often independent parts in accordance with the
National Research Council (NRC) paradigm: hazard
identiﬁcation, exposure assessment, dose–response
assessment, and risk characterization.
risk assessment (CRA) is the analysis, characteri-
zation, and possible quantiﬁcation of the combined
risks from multiple stressors via multiple exposure
routes (the ways individuals physically contact the
chemicals, e.g., oral, inhalation, or dermal exposures)
in a deﬁned community or speciﬁc population.
Although some CRAs evaluate the risks posed
by a single type of stressor through multiple ex-
posure routes, such as speciﬁc pesticide classes
(e.g., organophosphates, N-methyl carbamates) or
dioxin-like compounds, other CRAs consider the
2017 Society for Risk Analysis