Occurrence & Exposure to Heavy Metals
Heavy metals (like cadmium, lead, arsenic, etc.) are natural constituents of the Earth’s crust and have existed on there since the Earth’s formation. Naturally, metals and other elements (e.g. potassium, iron) leech into fruits, vegetables, or any plant-based food grown directly in soil or surrounding bodies of water. Consequently, if these plants are used to feed livestock then the metals will leech into many animal or animal based products as well. Because of this, oral exposure of these metals is more ubiquitous than consumers realize. This environmental exposure impacts both organic and conventionally grown crops equally. So choosing organic will not necessarily minimize consumers’ exposure to metals.
In a similar manner, water obtained from natural springs would contain some of these heavy metals. In fact, a 2011 study in California found 14 heavy metals in six different sources of bottled natural spring water(1). All concentrations were within federal and state maximum contaminant levels, except for arsenic which exceeded California public health goal levels in all six sources.
In the ocean, seafood like tuna obtain mercury from the seabed. Cooking foods in iron or aluminum-made cookware might also leech trace amounts onto the food being cooked in them. Some metals are even used therapeutically in medications such as (but not limited to) gold, gallium and lithium. Moreover, dental amalgams made from silver and mercury and prosthetics made from metal alloys may further contribute to one’s daily exposure. All of these present possible sources of exposure via oral ingestion.
Non-oral exposure may also occur from common household items containing some of these metals. They include fertilizers, fungicides, batteries, household cleaning agents and lead-based paints. Industrial exposure is more common in adults working in facilities handling metals or near hazardous waste sites and accounts for the majority of heavy metal poisonings throughout human history (2).
While it is alarming for consumers to hear that the more plant-based foods they consume, the more heavy metals they might be exposed to, it is most important to remind them that the benefits of plant-based foods seem to far outweigh any consequences. Fortunately, the body is able to act as a natural buffer to these heavy metals as well.
- Sullivan MJ, Leavey S. Heavy metals in natural bottled spring water. J Environ Health. 2011 Jun; 73(10):8-13.
- Soghoian S, Tarabar A. Heavy metal toxicity. Medscape Reference. 2011. Available at: http://emedicine.medscape.com/article/814960-overview