For children, mercury exposure may lead to impaired brain development and consequent learning difficulties or a lower IQ, together with behavior problems. Exposure of pregnant women to mercury increases the risk of developmental problems in the fetus, such as impaired motor skills and speech development. Children under five years of age are particularly sensitive to toxic substances and therefore most vulnerable to mercury toxicity, which may affect their brain development.

Mercury can pose serious health risks to adults exposed to it. Neurological problems are most commonly reported. Symptoms include memory loss, a tremor, anxiety or depression. Adults with high or prolonged exposure to mercury can also be at risk for severe heart or kidney disease. With only a small amount ingested, mercury can build up over time to create health problems even from limited exposure.

Mercury can also affect animals and their habitat. Many wild and domesticated animals get exposed to mercury that can lead to serious health effects. Bird species exposed to mercury can experience reproductive failures, while fish populations may have reduced survival rates due to their accumulation of the toxic metal. For millions of Bangladeshis, fish is an important source of protein so this is a serious concern.

Once mercury enters the food chain, it can affect not only the animals that ingest it but also the people who eat them. As larger animals consume smaller ones that have already ingested mercury, the chemical concentration increases in the bodies of these predators through a process known as bioaccumulation. Eventually, top marine predators, such as sharks, have the highest concentrations of the toxin. But larger fish, like those that humans commonly eat, also contain high amounts of mercury. Regular consumption of these fish can lead to high levels of the toxin in the bodies of those who eat them — even if they don’t know it.