EPA IRIS — Lead, Oral RfD and Carcinogenicity Assessment
The EPA Integrated Risk Information System chemical assessment for inorganic lead does not derive a quantitative oral reference dose (EPA IRIS Pb 2004). The oral RfD section of the IRIS file (Section I.A.) contains a qualitative discussion only, last revised 2004-07-08, on the basis that available data do not support a traditional threshold-based RfD derivation for lead’s most sensitive endpoint (developmental neurotoxicity in children). The inhalation RfC (Section I.B.) is not evaluated. The carcinogenicity assessment (Section II.) was last revised 1988-09-26 and classifies inorganic lead as B2 (probable human carcinogen) based on animal evidence with inadequate human evidence; no cancer slope factor or unit risk is derived (EPA IRIS Pb 2004).
EPA’s operational position parallels JECFA’s 2010 withdrawal of the PTWI (JECFA 72nd 2010) and EFSA’s 2010 conclusion (EFSA Pb 2010): lead has no demonstrated effect threshold for the most sensitive endpoint, so traditional reference-value methodologies do not apply (EPA IRIS Pb 2004). US lead regulatory action operates through CDC blood lead reference values (CDC BLRV), FDA Closer to Zero Interim Reference Levels, and matrix-specific FDA action levels (FDA CTZ Pb 2025) rather than through an IRIS-derived oral RfD.
Assessment status
Assessment status from EPA IRIS Pb 2004:
| IRIS section | Status |
|---|---|
| Oral RfD (I.A.) | Not derived; qualitative discussion only, last revised 2004-07-08 |
| Inhalation RfC (I.B.) | Not evaluated |
| Carcinogenicity Assessment (II.) | Yes; last revised 1988-09-26 |
| Cancer classification | B2 (probable human carcinogen) |
| Cancer slope factor / unit risk | Not derived |
| File first on-line | 1988-03-01 |
Sources
- EPA IRIS Pb 2004 — EPA IRIS Chemical Assessment Summary, Lead and Compounds (Inorganic), CASRN 7439-92-1.