Health impacts of contaminants from fertilisers (Signal)

The widespread application of mineral fertilisers, sewage sludge and manure to agricultural soils is the main source of excess nutrient pollution in Europe (EEA, 2021). This can impact human health negatively by altering water and air quality, affecting food and water provision, and reducing recreational activities such as fishing and bathing (De Vries, 2021), as detailed in the first Zero Pollution Monitoring Assessment (EEA, 2022).

Additionally, mineral and organic fertilisers can be contaminated with substances of human health concern. In mineral fertilisers, these include heavy metal contaminants; in organic fertilisers, these include heavy metals, pathogens and substances of emerging concern such as persistent organic pollutants, pharmaceuticals and microplastics (see signal Long-term impacts of sludge spreading on agricultural land).

When fertilisers are applied to land, there are several potential routes to human exposure. A key pathway is via food products, as crops can bioaccumulate harmful contaminants. Contaminants and pathogens can also enter watercourses, leading to the ingestion of contaminated water or fish, or through direct skin contact. Pathogens can also enter the human food chain when organic fertilisers are applied.

Certain contaminants and secondary fertiliser compounds have adverse effects on human health, including neurotoxicity, infectious diseases, carcinogenicity and endocrine-disrupting effects. For example, cadmium, a heavy metal contaminant of both organic and inorganic fertilisers, is a classified carcinogen (ECHA, undated).

However, the direct risk to humans posed by fertilisers depends on various conditions along the exposure pathway and the presence of other sources of environmental contamination makes estimates difficult. In addition, concerns are growing that antimicrobial residues contained in manure and sewage sludge could also drive the emergence and spread of antimicrobial resistance (AMR) genes in soils (Larsson and Flach, 2022; Chen et al., 2016).

At present, all EU Member States have set limits for heavy metals in sewage sludge used in agriculture and some have regulated additional pollutants (EC, 2022). The limits set are generally much lower than those contained in the Sewage Sludge Directive (Anderson et al., 2021), which was adopted nearly four decades ago and does not mention other important substances such as persistent organic pollutants, pharmaceuticals and microplastics (EC, 2023). The 2019 Fertilising Products Regulation (EU, 2019) also set limit values for a series of contaminants in both organic and mineral fertilisers available from the EU market.

Nevertheless, in the absence of systematic EU-level or national monitoring of contaminants in mineral fertilisers, sewage sludge and manure, it is not currently possible to estimate the burden of disease related to the application of fertilisers in Europe.

Some national-level studies have focused specifically on the long-term risks related to contaminants in sewage sludge or manure re-applied on land. For example, field trials conducted in Sweden since 1981 have found that quantities of heavy metals contained in sludge have reduced significantly over the past four decades, with an average decrease of 85% for metals such as mercury, cadmium, copper, lead and zinc. Sludge application also did not affect levels of heavy metals in soils (Kirchmann et al., 2017; Naturvårdsverket, 2015; Hushållnings sällskapet, 2021). The same trials also suggested that the long-term application of sewage sludge did not cause the accumulation of antibiotics or enrichment of AMR genes in soils (Rutgersson et al., 2020).

More generally, contaminants in fertilisers may pose an indirect risk to human well-being through their negative impact on water, air and soil quality, and important ecosystem services.

In Europe, encouraging the safe use of organic fertilisers (i.e. ensuring fertilisers do not contain harmful levels of pathogenic organisms) could contribute to circularity in food systems and reduce reliance on imported mineral fertilisers. This would entail upstream approaches to reduce the contamination of sludge and manure, and the application of management technologies to recover nutrients, such as phosphorus from incinerated sewage sludge ash (Anderson et al., 2021).

Please consult the relevant indicators and signals below for a more comprehensive overview on the topic.