Soil analysis studies in the arsenic- and lead-tainted orchards of Massachusetts have revealed that the two metals “Pb and As bind ‘tightly’ to soil HA [humic acids] molar mass fractions.”42
A study in Taiwan found an important relationship between the geographical concentrations of leading heavy metals, including arsenic and nickel, and the prevalence of oral cancer in patients who smoked or chewed betel quid (a combination of betel leaf, areca nut, and slaked lime). That is, cancer and other malignancies predominated in areas where the soil was contaminated with those elements.43
TOXIC ELEMENTS IN FERTILIZERS
The prevalence of heavy metal compounds in most fertilizers used in agriculture today poses ongoing problems for the bioaccumulation of toxins in crops, animals, humans, and the rest of the food chain.1
Naturally occurring elements and heavy metals (including mercury, lead, cadmium, and arsenic) are frequently found in combination with some of the world’s leading industrial ores. This means that mining and processing those ores brings to the surface of the planet toxic elements that would have otherwise stayed buried.
Such is the case with phosphorous, which, alongside nitrogen and potassium, is one of the most important macronutrient constituents used in the creation of fertilizers. Phosphate ore typically contains cadmium in concentrations as high as 300 mg/kg, with sedimentary rock containing the highest concentrations. Other hazardous metals such as lead, nickel, and copper are also abundant in phosphate ores.2,3
As the primary application of phosphate ore is in the creation of fertilizers, its contamination by cadmium means a significant amount is added to the soil, creating abundant opportunities for human exposure to the known carcinogen and environmental toxin, especially through dietary uptake of foods and the inhalation of tobacco smoke.4
However, while phosphate fertilizers contribute a significant quantity of metals—particularly cadmium—to the soil, it is not the number one contributor. It may surprise many to know that industrial waste and sewage sludge is also exploited as a source of fertilizer, and contributes vastly higher quantities of heavy metals and other toxins to soils, and ultimately human intake, than nonwaste fertilizers ever could.5
EPA Okays Selling of Sewage Sludge
The wet, solid cake that remains after wastewater treatment plants process industrial and residential waste has long been referred to as sewage sludge. Decades ago, it was common practice for many municipalities—particularly very large urban areas—to haul the sludge and dump it into oceans and waterways, until the practice was banned by the EPA in 1992.6
In the mid-1990s, two lobbying groups—the U.S. Composting Council (USCC) and the Water Environment Federation (WEF)—joined forces with the EPA to promote the use of sewage sludge as a safe, effective, and cheap fertilizer under the rebranded name “biosolids.” It was actively promoted by many agencies as an effective way to dispose of human waste, while creating a viable by-product market.7
In 1997, the EPA said their “longstanding policy encourages the beneficial reuse and recycling of industrial wastes, including hazardous wastes, when such wastes can be used as safe and effective substitutes for virgin raw materials.”8
A study on the bioavailability of cadmium and its accumulation in soils found that while continued phosphate fertilization raised cadmium levels, the increase was much lower than those observed from the application of sewage sludge as fertilizer, both in overall accumulation as well as in bioavailability to Swiss chard and other plants.9
Heavy metals in biosolids can be a particularly worrisome issue, as the toxic elements frequently found in drinking water, food, and medicine tend to concentrate in the biosolids that are routinely applied to soils as fertilizer. There, they accumulate in the soil, leading to a persistent rise in toxic elements taken up by food crops.
Biosolids from sewage waste can contain especially high levels of accumulated metals—from lead, to cadmium, to mercury, to arsenic, or others such as nickel, copper, aluminum, or tin.10
In February of 2016, I acquired a bag of “Dillo Dirt” from the city of Austin, Texas, and I tested it for heavy metals via ICP-MS instrumentation. Dillo Dirt is composted human sewage that’s purchased by landscapers and home gardeners for use on lawns and gardens. Even though the bag says, in small print, that it’s not sold for use on edible vegetable gardens, it is positioned on retail shelves as a garden compost product (and no one reads the small print on a bag of compost anyway).
As you might expect, my ICP-MS analysis showed that Dillo Dirt was heavily contaminated with every toxic element tested, including lead, mercury, cadmium, arsenic, and copper. An organic chemistry analysis conducted by my colleague via LC/MS also revealed shockingly high levels of a chemical fungicide in the compost product.
Mercury used in dental amalgams poses a particularly significant source of concentrated metal exposure and environmental pollution through biosolids, as most dental practices have, for decades, used municipal water for waste disposal, and have been recognized as a significant contamination source.11,12
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
