Estimates by the World Health Organization found that about one-third of mercury waste collected in sewage sludge substrate is derived from dumping amalgam fillings and related occupational implements. Moreover, many of the methods that have been implemented to separate dental mercury from wastewater were found to be inadequate.13
Once elemental mercury, used in dentistry, reaches waterways from direct dumping into groundwater, lakes, and streams, or indirectly from runoff on land tilled with biosolid fertilizer inputs, microbes readily convert it to methylmercury, which infamously bioaccumulates up the food chain in many fish and seafood, eventually reaching humans and others near the top of the food chain (see section on “Methylmercury in fish” on page 49 for more information).14
Biosolids from sewage sludge are now being increasingly produced and sold by most larger cities in the United States, and are increasingly used as a cheap and readily available source of fertilizer for crops intended for human and animal consumption. This poses numerous problems, including introducing a source of concentrated heavy metals as well as pharmaceutical, antibiotic, industrial, and medical waste, plus a multitude of pathogens, bacteria, viruses, and superbugs into the food chain.15
Cornell University conducted a 1981 report titled “Organic toxicants and pathogens in sewage sludge and their environmental effects,” which found more than 60,000 toxic substances and chemical compounds of concern in sewage remains. In 1988, the U.S. Environmental Protection Agency conducted a National Sewage Sludge Survey, identifying 400 pollutants commonly concentrated in sludge that posed the greatest hazards for large cities; later, in 2001, the EPA followed up with monitoring the levels of carcinogenic dioxins and dioxin-like compounds commonly found in sludge. The possibilities of interaction and further amplification by any or all of these toxic elements and compounds is understudied and unknown, but they present a clear and present risk to public health and safety.16
Industrial waste from animal feeding operations, and livestock manure in general, is also a source of metals contamination.17
Arsenic has for many decades been added to the diets of broiler chickens, as well as pigs, turkeys, and other animals, to promote growth. The resulting litter of chickens and other livestock, rich in arsenic compounds, is frequently used as a cheap and readily available fertilizer that the industry would otherwise have to dispose of at great cost.18
Cow and pig manure from factory farms used as biofertilizers contains concentrated metals and toxic elements. In China, this situation has become especially severe, with copper, arsenic, and zinc bioaccumulating through animals, manure, and soils. Chicken waste is the most significant source of metal pollution from manure in China, as in the United States, due to the deliberate addition of arsenic.19,20,21
Reusing excrement from both livestock and human populations is an age-old practice, but never before in history have these by-products included so many hazards in one application.
Cattle sludge from Concentrated Animal Feeding Operations (CAFO) add to the soil other pollutants such as antibiotics, pharmaceutical compounds, hormone mimickers, and hundreds of types of bacteria, which carry their own potential risks (see the “Animal Feed Contaminants” section on page 185 for more information). Many critics of CAFO practices believe this sludge by-product to be a potential culprit in recent E. coli outbreaks in the nation’s produce.22
Arsenic-treated wood
About 90 percent of the arsenic produced for industrial purposes is ultimately used in wood preservation in the form of chromated copper arsenic (CCA). While CCA has now been phased out, it still permeates much of the existing infrastructure. This arsenic compound has been used in lumber treatment to both prevent rotting and to act as an insecticide that kills termites, ants, and other unwanted pests.
This arsenic-treated wood has been almost universally used in utility poles and for fencing and wooden decks around businesses and residences.44 The Federal Insecticide, Fungicide, and Rodenticide Act now prohibits the use of CCA-treated wood in residential areas, but decades of nearly ubiquitous use has left an enormous exposure footprint on the environment.
The EPA has warned parents not to allow their children to play anywhere on, under, or even near patios and decks that were built with arsenic-treated wood, as the highly toxic arsenic compound is known to leach into the surrounding dirt or soil, as well as the surrounding landscape and any water sources.
Even worse, CCA-treated wood also contains chromium VI, better known as hexavalent chromium, the element that caused so many people in Hinkley, California, to get sick after industrial contamination (as portrayed in the based-on-a-true-story film Erin Brockovich starring Julia Roberts). Hexavalent chromium leaches into the environment at greater levels than arsenic and is considered a genotoxic carcinogen, meaning that it is linked with both cancer and damage to the DNA structure itself.
In addition to these concerns are neighborhood fences, electric poles, picnic tables, and playgrounds. In conjunction with its facilitation of the lumber industry’s voluntary “phasing out” of what was once widespread CCA treatment, the EPA has provided oversight for “focusing on children” by assessing “the potential exposure of children to playground equipment built with CCA-treated wood” since 2001, while considering ways to deal with the countless structures in society that were built with components saturated in this harmful compound.45
Testing performed in areas around utility poles that had been heavily coated with a CCA treatment has confirmed that significant levels of both arsenite and arsenate had leached into soils and groundwater in the area.46
Some mitigation treatments have successfully converted the toxic inorganic arsenic trioxide to a less harmful pentavalent arsenate form; however, this form readily competes with phosphorous inside the body and thus has been known to impair essential bodily functions.
As far back as 1972, the EPA knew of the toxicity issues with arsenic-based pressure treatments and injection treatments including arsenic acid, arsenic pentoxide dehydrate, sodium arsenate, sodium hydroarsenate, and disodium arsenate, but the agency considered the implications of the loss of use to be a “national disaster” and thus downplayed the real environmental implications.
Arsenic in food
More than a century ago, it was arsenic that helped pave the way for modern reforms to clean up the food supply. In a case in Bradford, England, in 1858, which later spurred the Pharmacy Act of 1868, a sweetshop worker misidentified and then accidentally mixed some 12 pounds of arsenic trioxide into delicacies. Even though several of the experienced workers thought the sweets looked odd, they were still sold, prompting one vendor to demand a discount. Subsequently, twenty people were ultimately killed and at least two hundred others were sickened.47 This haphazard poisoning opened the door to regulations that took on food adulteration as a major issue.
Though subsequent regulation has banned the use of many arsenic-based pesticides and curbed some of the chemical’s industrial use, arsenic accumulation in the soil has thoroughly contaminated many areas throughout the world, thus severely affecting the food supply. Even low levels have shown carcinogenic effects through chronic exposure, raising serious concerns about staple food crops.
This problem is compounded by the volume of food exports coming from China and other countries where environmental standards are often lax.
By far the biggest source of total arsenic in foods comes from seafood, including fish, crustaceans, and seaweed. The CDC reports that the “biological half-life of [organic] ingested fish arsenic in humans is estimated to be less than 20 hours, with total urinary clearance in approximately 48 hours.”48 Most researchers have dismissed the role of organic sources of arsenic in causing any harm, but inorganic forms are widely recognized as being harmful to human biology. This difference is why a key question we’re examining in our forensic laboratory