Risk estimates are calculations based on models - they are useful for ranking purposes but are not necessarily predictive of any actual individual's risk of getting cancer or other diseases.
SCORECARD'S RISK ASSESSMENT METHODS
Scorecard utilizes conventional risk assessment methods to estimate the potential health risk associated with outdoor exposures to hazardous air pollutants. In general, Scorecard's methods are in accordance with EPA's Cancer Risk Guidelines and California's AB 2588 Health Risk Assessment Guidelines. To generate screening-level health risk estimates, Scorecard combines its risk assessment values with chemical doses estimated from ambient air concentrations using standard exposure assessment assumptions.
Cancer risks are assessed for each pollutant by multiplying the estimated dose of a chemical that a average individual would receive from its predicted concentration by its cancer potency to derive an upper bound estimate of added cancer risk. Cancer risks for each hazardous air pollutant were assumed to be additive and were summed together to derive an estimate of total added lifetime cancer risk. More on Scorecard's cancer risk measures.
Noncancer health risks are assessed by dividing the estimated dose of a chemical that a average individual would receive from its predicted concentration by its reference concentration to derive a hazard index. A hazard index greater than one indicates that outdoor concentration estimates exceed the reference concentration and may be of concern for noncancer effects. Cumulative noncancer hazard was calculated by summing together the hazard indices for all pollutants with chronic noncancer hazard indices. Noncancer hazards to specific target organ systems is also evaluated by calculating separate hazard indices for subsets of pollutants associated with specific noncancer health effects (such as immunotoxicity, neurotoxicity, etc.) More on Scorecard's noncancer risk measures.