MERCURY

Overview

CAS number

7439-97-6

Functional Class

Food Contaminant
METALS

Evaluations

Evaluation year: 2011

Comments:

Committee agreed that the toxicological database for mercury(II) chloride was relevant for assessing the health risk of foodborne inorganic mercury. Kidney effects are consistently observed in various experimental species (weight changes, proximal tubule damage and progressive nephropathy). The Committee considered kidney weight changes, which occurred at doses similar to or lower than other renal effects, the critical endpoint and 6-month exposure to be sufficient to establish a health-based guidance value, given that steady-state renal mercury concentrations were reached by 4–6 months in rats dosed via their drinking water (NTP, 1993) and exposures in the same dose range for longer durations produced early mortality. Although the NTP (1993) bioassay provided limited evidence for carcinogenicity; however, direct reaction of mercury(II) chloride with DNA has not been demonstrated. Therefore, setting a health-based guidance value was considered appropriate. The BMDL10 for relative kidney weight increase in male rats was 0.11 mg mercuric chloride/kg bw/d, corresponding to 0.06 mg/kg bw/d as mercury after adjustment for the 5 days/week dosing schedule used in the study & for the molar percent of mercury in mercury(II) chloride. After application of a 100-fold uncertainty factor, the Committee established a PTWI for inorganic mercury of 4 µg/kg bw. The previous PTWI of 5 µg/kg bw for total mercury was withdrawn. The new PTWI for was considered applicable to dietary exposure to total mercury from foods other than fish and shellfish. The upper limits of estimates of average dietary exposure to total mercury from foods other than fish and shellfish for adult (1 μg/kg bw per week) and for children (4 μg/kg bw per week) were at or below the PTWI.

Intake:

The 90th-percentile limits of estimates of average dietary exposure to total mercury from foods other than fish and shellfish for adults (1 μg/kg bw per week) and for children (4 μg/kg bw per week) were at or below the PTWI for inorganic mercury.

Tolerable Intake:

PTWI: 4 µg/kg bw

Meeting:

Report:

TRS 959-JECFA 72

Tox Monograph:

72nd_2011_Mercury.pdf

Toxicological study

Pivotal Study:

Inorganic [Hg(II)Cl], 6 month drinking water study (NTP, 1993): Rats & mice (n=10 rats or mice/sex/group) were gavaged with mercuric (II) chloride for 26-27 weeks at doses of 0, 0.312, 0.625, 1.25, 2.5, or 5 mg/kg bw/d (rats) or 0, 1.25, 2.5, 5, 10, or 20 mg/kg bw/d (mice). There was no NOEL for the effect of increased kidney weight parameters in rats.

Animal Specie:

Fischer rats and B6C3F1 mice

Effect:

Kidney weight changes, proximal tubule damage and progressive nephropathy

NOAEL:

none

LOAEL:

Not determined

PTWI:

4 µg/kg bw

Point of departure:

BMDL10: 0.06 mg/kg bw/day

Evaluation year: 1978

Tolerable Intake:

PTWI 0.005 mg/kg bw

Meeting:

Report:

TRS 631-JECFA 22/26

Tox Monograph:

FAS 13-JECFA 22/43

Previous Years:

1972, NMRS 51/TRS 505-JECFA 16/11, FAS 4-JECFA 16/11. PTWI 0.005; ADI: NONE 1970, NMRS 48/TRS 462-JECFA 14/18. NO ADI 1966, NMRS 43/TRS 373-JECFA 10/16