title: Toxicity reference values and tissue residue criteria for protecting avian wildlife exposed to methylmercury in China.
abstract: MeHg is the most biologically available and toxic from of mercury, and has the potential to bioaccumulate and biomagnify as it moves up the food chain. These characteristics result in MeHg exposure to avian wildlife at high trophic levels that can produce adverse effects. The toxicity of MeHg to birds was reviewed, and using available data, TRVs and TRCs were derived for protecting birds in China. The TRV and TRC values were based on concentrations of MeHg in diet (or fish tissue based) and tissues of birds. Two methods were applied to derive TRVs from concentrations in the diet or in tissues. These were the CSA and SSD approaches. Results of published studies show that reproductive productivity of while ibis was the most sensitive endpoint for MeHg exposure, and study results on white ibises were used for deriving the TRV and TRC values, which included applying a UF of 2.0. For the SSD approach, data for ten species were used to construct the SSD for MeHg, and to calculate the dietary-based TRV and TRC values. Using the CSA approach, the TRV was based on MeHg in the diet and was derived as 5.0 ng MeHg/g (bm).day; for feathers and blood, the TRV's were 3.16 μg THg/g (wwt), and 0.365 μg THg/g (wwt), respectively. The corresponding TRCs were 15.47 ng MeHg/g (wwt), 3.16 μg THg/g (wwt)respectively. The dietary-based TRV and TRC derived by SSD were 3.09 ng MeHg (bm)/day and 9.56 ng MeHg/g (wwt) respectively. However, birds tissue residue-based criteria were not available because insufficient MeHg effects data existed to construct an SSD for birds. We compared the criteria derived in our study to those developed by others, and concluded that our results provided more reasonable protection to Chinese avian wildlife. By comparing the criteria derived values we calculated to actual MeHg levels in fish and bird tissues, we concluded that these criteria values are useful indicators for screening-level risk assessments of avian wildlife in Chinese aquatic systems. The results of this meta-analysis might therefore have important implications for assessing the risk of Hg exposure to birds and for environmental management in China and in other regions. Moreover, because humans and top avian wildlife consumers are at the same trophic level, these criteria may also be used as a reference for human health risk assessment. The diet of birds consists of aquatic species from different trophic levels. However, the structure of the food web for avian wildlife and the environmental factors that effect their exposure to MeHg vary among aquatic systems. Therefore, further research results are needed on the food web structure of avian wildlife in Chinese aquatic systems to provide more insight into what constitutes adequate protection for avian wildlife.
authors.affiliation: Guangzhou Institute of Geochemistry, Chinese Academy of Science, China.
authors.forename: Ruiqing
authors.initials: R
authors.lastname: Zhang
authors.forename: Fengchang
authors.initials: F
authors.lastname: Wu
authors.forename: Huixian
authors.initials: H
authors.lastname: Li
authors.forename: Guanghui
authors.initials: G
authors.lastname: Guo
authors.forename: Chenglian
authors.initials: C
authors.lastname: Feng
authors.forename: John P
authors.initials: JP
authors.lastname: Giesy
authors.forename: Hong
authors.initials: H
authors.lastname: Chang
mesh_terms: D000818:Animals; D000835:Animals, Wild; D002681:China; D004781:Environmental Exposure; D004785:Environmental Pollutants / Q000633:toxicity*; D008767:Methylmercury Compounds / Q000633:toxicity*
chemical_list: D004785:Environmental Pollutants; D008767:Methylmercury Compounds