Methylmercury
methylmercury, methyl mercury, MeHg, mercury, metilmercurio
What it is
Methylmercury is a form of mercury that builds up through aquatic food chains. Fish absorb it from what they eat, so large, long-lived predators can contain much more than smaller species.
Why BOTIA flags it
Methylmercury binds to proteins in the body and reaches the nervous system, where it can damage coordination, vision and sensation; the developing brain is the most vulnerable. It crosses the placenta: cord blood can contain higher concentrations than maternal blood, and methylmercury also passes into breast milk. In the food chain it builds up most in large, long-lived predators — swordfish, shark and large tuna — so the practical message is not to stop eating fish, but to choose lower-mercury species. JECFA set a provisional tolerable weekly intake of 1.6 µg/kg body weight for methylmercury to protect the developing nervous system.
BOTIA CAN
- Explain why large, long-lived predatory fish tend to contain more methylmercury than smaller species.
- Explain why the Woman layer matters: methylmercury crosses the placenta, cord blood can contain more than maternal blood, and exposure can continue through breast milk.
BOTIA CANNOT
- Measure the methylmercury concentration of a particular fish or food from its ingredient list.
- Calculate a person's weekly methylmercury exposure or determine how much reached a fetus or infant from one label.