Cognitive performance of children prenatally exposed to "safe" levels of methylmercury

Environ Res. 1998 May;77(2):165-72. doi: 10.1006/enrs.1997.3804.


Within a cohort of 1022 consecutive singleton births in the Faroe Islands, we assessed prenatal methylmercury exposure from the maternal hair mercury concentration. At approximately 7 years of age, 917 of the children underwent detailed neurobehavioral examination. Little risk is thought to occur as long as the hair mercury concentration in pregnant women is kept below 10-20 microg/g (50-100 nmol/l). A case group of 112 children whose mothers had a hair mercury concentration of 10-20 microg/g was therefore matched to children with exposure below 3 microg/g, using age, sex, time of examination, and the mother's score on Raven's Progressive Matrices as matching criteria. The two groups were almost identical with regard to other factors that might affect neurobehavioral performance in this community. On six neuropsychological test measures, the case group showed mild decrements, relative to controls, especially in the domains of motor function, language, and memory. Subtle effects on brain function therefore seem to be detectable at prenatal methylmercury exposure levels currently considered to be safe.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Case-Control Studies
  • Child
  • Cognition / drug effects*
  • Cognition / physiology
  • Eye Movements / drug effects
  • Eye Movements / physiology
  • Female
  • Fingers / physiology
  • Hand / physiology
  • Humans
  • Male
  • Maternal Exposure / adverse effects*
  • Maximum Allowable Concentration
  • Mercury / administration & dosage
  • Mercury / adverse effects
  • Mercury Poisoning / etiology
  • Mercury Poisoning / physiopathology
  • Mercury Poisoning / psychology
  • Methylmercury Compounds / administration & dosage
  • Methylmercury Compounds / adverse effects*
  • Motor Activity / drug effects
  • Motor Activity / physiology
  • Movement / drug effects
  • Movement / physiology
  • Neuropsychological Tests
  • Psychomotor Performance / drug effects*
  • Psychomotor Performance / physiology
  • Reaction Time / drug effects
  • Reaction Time / physiology


  • Methylmercury Compounds
  • Mercury