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What Sewage Sludge Toxins may be in Your ‘Natural’ Pet Food?

Sewage sludge contains all sorts of household and industrial toxins which are flushed down the toilet or private and industrial drains. How could this possibly impact the quality of your ‘natural’ pet food?

Just to remind you: the term ‘natural’ isn’t regulated and the best way to actually get a natural pet food when you want one is to buy a certified organic pet food, which among other things, wouldn’t contain sewage sludge-grown crops or animal ingredients. Verification by an independent party, an organic certification agency, is your guarantee that this is the case.

Non-certified organic pet foods contain so-called ‘conventional’ (i.e., non-certified organic) ingredients. Conventional agriculture routinely uses sewage sludge (also called ‘biosolids’) as ‘fertilizer.’ Every year more than half of the roughly 7 million metric tons of the biosolids produced in the United States are applied as fertilizer to farm fields.

The large amount of human waste processed in sewage plants means that sewage sludge contains high concentrations of phosphates and nitrates, which are desirable components of fertilizers. However, this sludge also contains highly toxic materials such as fluorides, industrial solvents, heavy metals, hormones, antibiotics, and even radioactive waste which may accumulate in the plants that are grown on sludge-fertilized farmland, as well as in the animals that are fed sludge-treated crops.


Here are just some of the many toxins that were detected by the EPA in sewage sludge from 74 randomly selected publicly owned water treatment/sewage sludge plants in 35 states (Targeted National Sewage Sludge Survey Report, 2009).

For understandable reasons, the EPA study had to limit the analysis to relatively few toxins; it is likely that sewage sludge contains many more toxins that have not been included in the EPA study.

‘Class B biosolids,’ which are the principal type of biosolids applied to land, also contain a variety of enteric pathogens (e.g., E.coli, salmonella). These were also not included in the recent EPA study.

At the end of this page you can find information on some of these toxins (marked in the text with numbers in parenthesis) and the health problems with which they are known to be associated.

1. Metals

Twenty seven of the 28 metals analyzed were found in every sewage sludge sample. The most prevalent were barium(1), beryllium(2), manganese(3), molybdenum(4), and silver(5). The other metals included: aluminum, antimony, arsenic, boron, cadmium, cobalt, lead, mercury, selenium, thallium, tin, vanadium, yttrium, and zinc.

Remember that elemental metals often are very toxic while they are life-sustaining in the forms in which they occur naturally in foods.

2. “Organics”

Of the six organics analyzed, four were found in at least 72 samples, one was found in 63 samples, and one was found in 39 samples. The most prevalent ‘organics’ are: pyrene(1), fluoranthene(2), 4-Chloroaniline(3).

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