Microplastics entering the food chain through biosolid fertilisers 

7 September 2022 Read the paper

Professor Andy Ball and Associate Professor Suzie Reichman discuss key issues that need to be taken into account when developing policy and regulatory options to address the accumulation of these contaminants.

The increasing use of biosolids as agricultural fertilisers may be causing microplastic pollution in Victoria, according to a recently published research note from the Victorian Parliamentary Library. 

Biosolids are treated sewage sludges derived from wastewater processing. While they have a range of uses, nearly three-quarters of biosolids are used in agriculture. 

They’re effective in topsoil rehabilitation and as a fertiliser that contains macronutrients like nitrogen, phosphorus, potassium, and sulphur and micronutrients, including copper, zinc, calcium, magnesium. 

But they also potentially contain a range of pollutants including microplastics, as well as some chemicals and pathogens. 

Microplastics and nanoplastics (MNPs) are tiny plastic particles, like the microbeads that are commonly added to a range of health and beauty products or fragments of larger plastics that have been broken down. These make their way from households via kitchens, laundries, bathrooms and in industrial effluents, and storm water to the wastewater system, where they are ubiquitous. 

Larger plastic items are removed during wastewater processing, but smaller particles are much harder to remove and remain in the biosolids that are then used as fertilisers subsequently contaminating the soil. 

From there the MNPs accumulate in plant root systems and enter the food chain. 

While not all researchers agree that MNPs affect human health, some research suggests that MNP exposure may harm people via physical and chemical pathways, particularly impacting the nervous system, respiratory system, kidney system, digestive and excretory system, placental barrier, and skin.