Assessing Human Health Response in Life Cycle Assessment Using ED₁₀s and DALYs: Part 2—Noncancer Effects

Abstract

In Part 1 of this article we developed an approach for the calculation of cancer effect measures for life cycle assessment (LCA). In this article, we propose and evaluate the method for the screening of noncancer toxicological health effects. This approach draws on the noncancer health risk assessment concept of benchmark dose, while noting important differences with regulatory applications in the objectives of an LCA study. We adopt the centraltendency estimate of the toxicological effect dose inducing a 10% response over background, ED10, to provide a consistent point of departure for default linear low-dose response estimates (betaED10). This explicit estimation of low-dose risks, while necessary in LCA, is in marked contrast to many traditional procedures for noncancer assessments. For pragmatic reasons, mechanistic thresholds and nonlinear low-dose response curves were not implemented in the presented framework. In essence, for the comparative needs of LCA, we propose that one initially screens alternative activities or products on the degree to which the associated chemical emissions erode their margins of exposure, which may or may not be manifested as increases in disease incidence. We illustrate the method here by deriving the betaED10 slope factors from bioassay data for 12 chemicals and outline some of the possibilities for extrapolation from other more readily available measures, such as the no observable adverse effect levels (NOAEL), avoiding uncertainty factors that lead to inconsistent degrees of conservatism from chemical to chemical. These extrapolations facilitated the initial calculation of slope factors for an additional 403 compounds; ranging from 10(-6) to 10(3) (risk per mg/kg-day dose). The potential consequences of the effects are taken into account in a preliminary approach by combining the betaED10 with the severity measure disability adjusted life years (DALY), providing a screening-level estimate of the potential consequences associated with exposures, integrated over time and space, to a given mass of chemical released into the environment for use in LCA.

Critical review of methodology and application of risk ranking for prioritisation of food and feed related issues, on the basis of the size of anticipated health impact

“…Five references presented methodology central to risk ranking and disease burden estimation Hofstetter, 2002;Mangen et al, 2010;Mangen et al, 2014;Pennington et al, 2002).…”

“…Approach: When applying DALY/QALYs in risk ranking, different methodologies must usually be applied to estimate incidences of disease and probability of relevant health outcomes depending on the hazards to be evaluated Hofstetter, 2002;Mangen et al, 2010;Mangen et al, 2014;Pennington et al, 2002 …”

“…A method for cumulative risk assessment of waterborne contaminant is presented where; toxicity measures are estimated for non-cancer and cancer effects separately, based on RfDs and Cancer Slope Factors, and in one case used for a life cycle assessment Pennington et al, 2002); DALYs per case are estimated for non-fatal disease outcomes by multiplying DALY severity scores with the expected lifespan (80 years) and for fatal disease outcomes (cancer) years lost compared to the expected lifespan is estimated. The proportion and incidence of individuals at risk (toxicity x exposure x population at risk) is estimated and mean individual total DALY values are calculated by summing individual risk (DALYs) for each compound, and for the whole population at risk (Crawford-Brown, 2012;Etchie et al, 2013).…”

Prioritizing hazardous pollutants in two Nigerian water supply schemes: a risk-based approach

“…Crawford-Brown and Crawford-Brown 4 and Pennington et al 19 argue that measures of toxicity, such as the reference dose, acceptable daily intake, tolerable daily intake and minimal risk level, were developed for assessing the health risk of individual hazardous substances in a regulatory context, not for comparing hazards. Consequently, CrawfordBrown and Crawford-Brown proposed using the 1% benchmark dose as the metric of toxicity for the noncancerous effects of a substance.…”

“…19 For cobalt and manganese, we used the no-observable-adverse-effect level (NOAEL) and the lowest-observable-adverse-effect level (LOAEL), respectively, both of which are expressed in mg per kg per day. These algorithms all assume a linear relationship between dose and response.…”