Association between prenatal mercury exposure and pediatric neurodevelopment: The Japan environment and children's study

Shohei Kuraoka; Masako Oda; Takashi Ohba; Hiroshi Mitsubuchi; Miyuki Iwai-Shimada; Nozomi Tatsuta; Michihiro Kamijima; Kimitoshi Nakamura; Takahiko Katoh; Japan Environment and Children's Study (JECS) Group

doi:10.1016/j.scitotenv.2024.177489

Association between prenatal mercury exposure and pediatric neurodevelopment: The Japan environment and children's study

Sci Total Environ. 2024 Nov 13:957:177489. doi: 10.1016/j.scitotenv.2024.177489. Online ahead of print.

Authors

Shohei Kuraoka¹, Masako Oda², Takashi Ohba³, Hiroshi Mitsubuchi⁴, Miyuki Iwai-Shimada⁵, Nozomi Tatsuta⁵, Michihiro Kamijima⁶, Kimitoshi Nakamura⁷, Takahiko Katoh⁸; Japan Environment and Children's Study (JECS) Group

Affiliations

¹ The South Kyushu Okinawa Unit Center, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan; Department of Pediatrics, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan; Division of Nephrology, Massachusetts General Hospital, Harvard Medical School, Boston, USA. Electronic address: skuraoka@kuh.kumamoto-u.ac.jp.
² The South Kyushu Okinawa Unit Center, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan.
³ The South Kyushu Okinawa Unit Center, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan; Department of Obstetrics and Gynecology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan.
⁴ The South Kyushu Okinawa Unit Center, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan; Fukuda Hospital, Kumamoto, Japan.
⁵ Japan Environment and Children's Study Programme Office, National Institute for Environmental Studies, Tsukuba, Japan.
⁶ Department of Occupational and Environmental Health, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
⁷ The South Kyushu Okinawa Unit Center, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan; Department of Pediatrics, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan.
⁸ The South Kyushu Okinawa Unit Center, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan; Department of Public Health, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan.

PMID: 39528210
DOI: 10.1016/j.scitotenv.2024.177489

Abstract

Mercury pollution, including from its use during gold mining and refining, remains an important problem worldwide. In particular, methylmercury, a microbial alteration of mercury released into the environment, is a major environmental neurotoxicant. Although there has been growing concern about the health hazards of exposure to low levels of mercury, the effects of prenatal mercury exposure on neurodevelopmental outcomes in children have remained controversial. In the Japan Environment and Children's Study, a large-scale nationwide birth cohort study, we measured methylmercury and inorganic mercury concentrations in cord blood and conducted developmental scoring tests at ages 2 and 4 years. We then analyzed the associations between mercury levels in cord blood and neurodevelopmental outcomes. Measurements of cord blood obtained from 3822 participants revealed median values of 7.39 ng/ml (5th percentile: 2.95, 95th percentile: 18.1) and 0.25 ng/ml (5th percentile: 0.10, 95th percentile: 0.58) for methylmercury and inorganic mercury, respectively. Analyzing the association with fish consumption, bonito-tuna was most strongly correlated with both methylmercury and inorganic mercury in cord blood. Although the association between cord blood mercury and neurodevelopmental scores was subsequently examined in 3083 individuals, we found no significant association with either methylmercury or inorganic mercury. Further quartile group analysis based on methylmercury concentrations in cord blood revealed no concentration-dependent association between a prenatal mercury exposure and neurodevelopment in children. However, various factors influence neurodevelopment, and long-term observational studies that consider those covariates are necessary for a more definitive conclusion. Although the findings of our study provide important insights into the association between prenatal mercury exposure and neurodevelopment, further research is needed to make recommendations for safe mercury intake thresholds during pregnancy.

Keywords: Children; Mercury; Methylmercury; Neurodevelopment; Neurotoxicant.