90 12.9 Heavy Metals and Toxic Compounds
Mercury, lead, chromium, copper, cadmium, and arsenic are perhaps most significant. Mercury and lead are released into the environment from burning coal and fossil fuels, and by mining operations. Consumer products that contain lead, mercury, and other toxic metals end up in landfills which can leak into waterways. Lead from improperly disposed of batteries is a major contributor to lead contamination. Starting in the 1920‘s lead was used as an “additive” to gasoline to increase engine performance, but was found to be a toxic addition to air and soil pollution. It has been banned in most countries, but the lead is still finding its way into ocean waters. Lead and many other toxic compounds were also used in paints before being banned.
Mercury was used in gold mining and extraction, and in light bulbs, and used in many other industrial purposes, now mostly banned. Large quantities of mercury was mined in the New Almaden mercury mining district near San Jose, California. Over 65 million pound of mercury were extracted from the mines in the, nearly all of it was consumed in the gold fields along the western Sierra Mountains of central California and is a major contaminant in the Sacramento River system feeding into San Francisco Bay. Mercury is problematic in that it is concentrated in organisms highest in the food chain. In many areas, fish, such as tuna, have unsafe levels of mercury that, if over-consumed, can lead to mercury poisoning in humans. After WWII, a chemical process used to manufacture plastics released large quantities of mercury compounds into Minamoto Bay, Japan. The bio-accumulated mercury in fish that was the primary source of protein in the fishing community populations around the bay, nearly the entire population was sickened, many displaying severe neurological disorders.
Cadmium is used in non-rechargeable nickel-cadmium batteries, and is a major toxin in landfill waste waters. Both cadmium and arsenic are released by runoff from poorly managed mining operations, both past and present throughout the world today. Arsenic in a common natural contaminant in groundwater in some coastal regions. Various cancers and other diseases are linked to consuming contaminated water and food with high levels of arsenic.
Heavy metal pollutant come from many sources including mining, smelting, abandoned lead batteries and garbage, chromium from tanneries, and other local industrial sources mostly in impoverished urbanized areas where there is little or no regulation oversight. Modern electronic gadgets are host to many toxic metals and organometallic compounds and should be recycled (not thrown into landfills that may leak toxins). Research by world health organizations report that at least 100 million people worldwide suffer health effects or die from heavy-metal pollution each year.
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