Not all toxins in seafood are created equal, and not all forms are equally harmful. Arsenic and lead are naturally occurring elements that can enter oceans and freshwater through industrial discharge, mining, agricultural runoff, and groundwater contamination. Once in aquatic ecosystems, these metals are absorbed by algae and plankton, concentrated in small fish, and are magnified as they move up the food chain. This bioaccumulation process means that even low levels of toxins in water can translate into much higher levels in the fish we eat.
The risk to human health depends on the chemical form of the arsenic and lead. For arsenic, inorganic species (arsenite and arsenate) are highly toxic and linked to cancer, cardiovascular disease, and developmental effects, while organic forms like arsenobetaine - common in most seafood - are largely non-toxic. Lead, however, has no safe threshold; it can impair neurological and cognitive development, especially in children.
Recent studies highlight regional hotspots, estuaries, lagoons, and aquaculture ponds near industrial zones, where fish often exceed WHO safety limits for arsenic and lead. Chronic exposure may also harm fish themselves, damaging organs and disrupting growth and reproduction, signaling broader ecosystem distress.
For consumers, experts advise diversifying seafood choices, checking local advisories, and avoiding high-risk species such as Hijiki seaweed or fish from contaminated waters. While seafood remains a nutrient-rich option in our diets, understanding the forms and sources of these metals, and supporting policies that reduce pollution at its source, are critical steps to ensure that what’s nourishing on our plates is also safe.
—Kyndra Shea