A review of the evidence to support interim reference level for dietary lead exposure in adults.

FDA developed the interim reference level (IRL) for lead of 3 µg/day in children and 12.5 µg/day in women of childbearing age (WOCBA) to better protect the fetus from lead toxicity. These IRLs correspond to a blood lead level (BLL) of 0.5 µg/dL in both populations. The current investigation was performed to determine if the IRL for WOCBA should apply to the general population of adults. A literature review of epidemiological studies was conducted to determine whether a BLL of 0.5 µg/dL is associated with adverse effects in adults. Some studies reported adverse effects over a wide range of BLLs that included 0.5 µg/dL adding uncertainty to conclusions about effects at 0.5 µg/dL; however, no studies clearly identified this BLL as an adverse effect level. Results also showed that the previously developed PTTDI for adults of 75 µg/day lead may not be health protective, supporting use of a lower reference value for lead toxicity in this population group. Use of the 12.5 µg/day IRL as a benchmark for dietary lead intake is one way FDA will ensure that dietary lead intake in adults is reduced.