Biosolids, pharmaceuticals and personal care products

​What's in biosolids

Biosolids are sewage solids that have been treated to eliminate harmful bacteria and reduce odours. Biosolids can also contain small amounts of other materials that come from household items and personal care products that we use, such as medications, soaps and shampoos. These products enter the wastewater system through our sinks and toilets.   

Do biosolids contain harmful materials?

To help answer this question, Metro Vancouver commissioned a human health risk assessment, which showed that human health risk from typical biosolids use is very low. For example, it would take 3,000 years for a worker applying biosolids to land 220 days/year to be exposed to the amount of the antibiotic ciprofloxacin that is considered harmful to human health. To look at it another way, it would take a child over 266,000 years of playing near, touching and digesting biosolids to be exposed to the amount of ibuprofen contained in one tablet of over-the-counter pain relief medication.

The compounds found in Metro Vancouver's biosolids are present in everyday items that most of us use on a daily basis and at much higher levels than are present in biosolids. As technologies improve, it is possible to measure these materials in biosolids in even trace amounts. However, research shows that the level or concentration of compounds is so low that it would take multiple lifetimes of working or playing around biosolids to equal everyday exposure to many common products, such as antimicrobials found in soaps and toothpaste, flame retardants found in fabrics, and pain relief medication.

Exposure to Biosolids Compared to Use of Common Products

Exposure to Biosolids Compared to Use of Common Products
It would take many years of working or playing around biosolids or landscaping soil containing biosolids to equal exposure to many common products.

 What is Risk Assessment?

A risk assessment estimates the risk to human health by examining how harmful a chemical is (toxicity) and the amount of contact with that chemical (exposure). RISK = TOXICITY x EXPOSURE

Chemicals with high toxicity and high exposure have higher risk, while chemicals with low toxicity and low exposure have lower risk.

This risk assessment followed the United States Environmental Protection Agency (U.S. EPA) risk assessment methodology.

Scenarios Gardener
(176 lbs)
Child (33 lbs) Hiker (176 lbs) Biosolids worker
(176 lbs)
Amount swallowed100 mg200 mg100 mg100 mg
​Contact frequency​52 days/year for 20 years​52 days/year for 6 years​12 days/year for 20 years​220 days/year for 25 years
​Parts of body in direct contact​Head, hands, forearms, lower legs, and feet​Head, hands, forearms, lower legs, and feet​Hands and arms​Hands and arms

 

These scenarios show the assumptions used for this risk assesment to calculate how many years these four individuals would need to be exposed to biosolids to get the equivalent exposure to chemicals in common consumer products.

The average person working or playing around biosolids or landscaping soil containing biosolids would not regularly get it all over their body, accidentally eat some of it, or intentionally drink muddy runoff water. However, this risk assessment overestimated exposure to ensure confidence in the results.