Aging municipal water pipes account for a significant amount of heavy metal toxicity in the supply of drinking water. These metal pipes, containing iron and other substances, corrode over time, allowing heavy metals to leach into the water flowing through them. Delivered community-wide for drinking and other uses, water from corroded pipes can carry unsafe levels of these metals, endangering human health.
Runoff from industrial sources, roads and landfills send highly concentrated levels of heavy metals, particularly iron, lead, nickel and mercury, into bodies of water worldwide. These sources account for most heavy metal toxicity in the oceans, endangering marine life across the food chain and introducing harmful levels of these metals, such as mercury, to the human food supply through fish such as tuna and salmon.
The movement of waters in streams and rivers carries heavy metals from the Earth's crust to the oceans. Stream erosion of rocks and mineral deposits adds naturally occurring metals such as copper, zinc and lead to sediment which eventually makes its way to the ocean. Combined with industrial and other runoff sources, stream and river runoff deposits significant amounts of heavy metals into the world's oceans.
Although humans need trace amounts of some heavy metals such as iron and copper for optimal health, higher levels of these metals can cause kidney and liver damage, high blood pressure and, as numerous studies of lead toxicity have demonstrated, developmental delays in children. In the oceans, organisms such as algae bioaccumulate heavy metals, which aids in monitoring the amounts of toxins entering the oceans and the threat to human health posed by water contaminated with these metals.