StableMercury Isotopes in Polished Rice (Oryza sativa L.)and Hair from Rice Consumers

摘要

Mercury (Hg) isotopic signatures were characterized in polished rice samples from China, U.S., and Indonesia (n = 45). Hg isotopes were also analyzed in paired hair samples for participants from China (n = 21). For the latter, we also quantified the proportion of methylmercury intake through rice (range: 31–100%), and the weekly servings of fish meals (range: 0–5.6 servings/weekly). For these participants, 29% (n = 6) never ingested fish, 52% (n = 11) ingested fish < twice/weekly, and 19% (n = 4) ingested fish ≥ twice/weekly. In rice and hair, both mass-dependent fractionation (MDF, reported as δ²⁰²Hg) and mass-independent fractionation (MIF, reported as Δ¹⁹⁹Hg) of Hg isotopes were observed. Compared to rice, hair δ²⁰²Hg values were enriched on average (±1 standard deviation) by 1.9 ± 0.61‰, although the range was wide (range: 0.45‰, 3.0‰). Hair Δ¹⁹⁹Hg was significantly inversely associated with%methylmercury intake from rice (Spearman’s rho = −0.61, p < 0.01, n = 21), i.e., as the proportionof methylmercury intake from rice increased, MIF decreased. Additionally,hair Δ¹⁹⁹Hg was significantly higher for participantsingesting fish ≥ twice/weekly compared to those who did notingest fish or ingested fish < twice/weekly (ANOVA, p < 0.05, n = 21); Overall, results suggest thatHg isotopes (especially MIF) in human hair can be used to distinguishmethylmercury intake from rice versus fish.