|Abstract Title:||Investigation of the Potential Subacute Developmental Toxicities of very Low Levels of Methylmercury in Mercury-contaminated Food Crops ? A Model Study|
|Presenter Name:||Sylvester Addai-Arhin|
|Company/Institution:||Prefectural University of Kumamoto|
|Session:||Progress in understanding Hg and human health impacts|
Abstract Information :
Methylmercury (MeHg) is known to cause developmental toxicities particularly, to the developing foetus following repeated prenatal exposures. Some studies have indicated that exposures to very low doses of MeHg can cause developmental toxicities in developing foetuses but other studies have presented contrary views. This study investigated the potential subacute developmental toxicities of very low MeHg levels in mercury-contaminated plantains and cassavas (food crops) following repeated prenatal exposures using Japanese medaka embryos as models. The embryos were exposed to methylmercury chloride concentrations corresponding to the average daily intake of MeHg in the food crops and were assessed for developmental toxicities following 18 days post-fertilization (dpf) exposures and 8 weeks post-hatch (wph) assessment. MeHg in concentration range of 0.87 ? 23.6 æg/L showed no toxicity to embryonic development of medaka at 18 dpf but showed increased larval mortality in concentration range of 3 ? 23.6 æg/L with an LC50 of 11 æg/L at 8 wph. Application of the one-compartment dose conversion model by USEPA and the maternal to cord blood MeHg ratio of 1:1.7 showed that MeHg in concentration range of 3 ? 23.6 æg/L corresponded to 0.20 ? 1.63 and 0.33 ? 2.76 æg/L maternal and cord blood MeHg levels following repeated prenatal exposures, respectively. The maternal and cord blood MeHg levels in this study are below the 5.8 æg/L by USEPA or the 3.6 æg/L by other researchers beyond which human foetal developmental toxicities may occur. Therefore, repeated prenatal exposures to very low levels of MeHg in the Hg-contaminated food crops may not be associated with any potential human foetal developmental toxicities.