Table 1.

Populations, exposures, comparators, outcomes (PECO) criteria.

PECO element	Evidence
Populations	Human: Any population and life stage (occupational or general population, including children and other sensitive populations). The following study designs will be considered most informative: controlled exposure, cohort, case–control, cross-sectional, and ecological. Case reports and case series will be tracked as “supplemental information.”
	Animal: Nonhuman mammalian animal species (whole organism) of any life stage (including preconception, in utero, lactation, peripubertal, and adult stages). Studies of transgenic animals will be tracked as mechanistic studies under “supplemental information.”
Exposures	Human: Any exposure to naphthalene (CASRN 91-20-3), including occupational exposures, via oral, inhalation, or dermal route[s].
	Animal: Any exposure to naphthalene (CASRN 91-20-3) via oral, inhalation, or dermal route[s]. Studies involving exposures to mixtures will be included only if they include an arm with exposure to naphthalene alone. Other exposure routes, including injection, will be tracked during title and abstract screening and tagged as “supplemental information.”
Comparators	Human: A comparison or referent population exposed to lower levels (or no exposure/exposure below detection limits) of naphthalene, or exposure to naphthalene for shorter periods of time.
	Animal: A concurrent control group exposed to vehicle-only treatment.
Outcomes	All health outcomes (both cancer and noncancer). In general, end points related to clinical diagnostic criteria, disease outcomes, histopathological examination, or other apical/phenotypic outcomes will be prioritized for evidence synthesis over outcomes such as biochemical measures.
PBPK	Studies describing PBPK models for naphthalene will be included.

Note: PBPK, physiologically based pharmacokinetic.