Heavy Metals in Fertilizers

The following page provides information about heavy metals in inorganic fertilizers. This information is based on screening evaluations conducted by the Minnesota Department of Health, and data collected by the Minnesota Department of Agriculture (MDA). MDA is the lead state agency responsible for testing and regulating fertilizers in Minnesota.

Background

The presence of heavy metals in inorganic fertilizers is well established.  Analytical testing of a wide range of fertilizer products shows that some phosphate and micronutrient fertilizers, and liming materials contain elevated levels of arsenic, cadmium, and lead compared to other fertilizer types (e.g., nitrogen, potash, gypsum).  A few waste-derived fertilizer products also have been shown to contain elevated (parts per trillion) levels of dioxins.

More than 54 million tons (110 billion pounds) of commercial fertilizers and liming materials were consumed in the US in 1996, with over 2 million tons consumed on farms in Minnesota.  The bulk of these fertilizers are applied in agricultural settings (croplands); however, some commercial fertilizers are used by consumers around the home (e.g., micronutrient and phosphate fertilizers applied on lawns and gardens).

Heavy metals occur naturally in soils and in source materials used to manufacture fertilizers.  In addition, heavy metals (and other hazardous constituents) occur in products as a result of blending fertilizers with recycled industrial wastes (e.g., steel mill flue dust, mine tailings).  Federal statutes allow reclassified industrial wastes to be used in the manufacture of fertilizers, provided that such use constitutes “beneficial recycling,” and that the concentrations of hazardous constituents in the resulting fertilizers do not exceed the treatment standards specified for wastes (40 CFR 266.20).

Risk assessments conducted by the US Environmental Protection Agency and others have concluded that the hazardous constituents in inorganic fertilizers generally do not pose risks to public health or the environment.  Of the large number of fertilizer products evaluated, only a few have been found to have contaminants at levels high enough to be considered a potential health concern (i.e., arsenic or dioxins in some micronutrient and liming materials).  Product testing by states, including Minnesota, generally has supported this conclusion. 

Screening evaluations and potential health risks

In 1999 MDH conducted a screening evaluation of heavy metals in fertilizers at the request of the MDA. The results showed elevated levels of arsenic, lead, and cadmium in some fertilizer products -- primarily micronutrient fertilizers (products that contain iron, zinc, and other nutrients that are added to soil to promote plant growth).

MDA requested that MDH conduct a follow-up screening evaluation in 2007-08 to assess new fertilizer data and risk assessments. MDH's evaluation used California Risk-Based Concentrations (CA RBCs) to screen fertilizer products for arsenic, cadmium, and lead.

MDH concluded that the hazardous constituents in inorganic fertilizers generally are not likely to pose risks to public health.  Of the large number of products that have been evaluated, only a few appear to be of potential concern (e.g., exposures to arsenic and lead in micronutrient fertilizers; and dioxins in a few products).  These products have low application rates, and they often are used in agricultural settings where the potential for young children to have direct contact with hazardous constituents is low (albeit possible). In addition, many of the products that were found to contain elevated levels of heavy metals are no longer licensed for sale in Minnesota.

MDH expressed concern about the potential for children to be exposed to elevated levels of lead in a few consumer products -- including some products below the California screening limits. Children have been shown to be especially vulnerable to the effects from exposures to lead (and potentially other heavy metals).  While several products tested by MDA are no longer licensed for sale in the Minnesota, these products may continue to be stored and used by consumers around the home.

At this time there are no product-specific data to evaluate the levels of dioxins in Minnesota metals in organic fertilizers and liming materials.  Based on available data, MDH cannot rule out the possibility that there are potential risks from dioxins in a few waste-derived Minnesota products. MDH has recommended that the MDA conduct testing of select (waste-derived) products for dioxins.

Fertilizer product data

MDA has tested a variety of micronutrient and phosphate fertilizer products for arsenic, cadmium, lead, and mercury. Several of these products are no longer licensed for sale in Minnesota.

Product specific information is available from other states at the links below:

• California Department of Food and Agriculture
• Fertilizer Product Database, Washington State Department of Agriculture
• Oregon Department of Agriculture
• Agriculture: Nutrient Management and Fertilizer. U.S. Environmental Protection Agency
• Background Report on Fertilizer Use, Contaminants, and Regulations (PDF), U.S. Environmental Protection Agency
• Fertilizer Materials Inspection Program, California Department of Food and Agriculture
• Metal Analysis, Washington State Department of Agriculture

Recommendations

Generally, MDH considers it prudent public health practice to avoid exposures to lead, arsenic and dioxins, where possible -- especially for susceptible populations, such as children. 

Product labels do not routinely provide information for consumers about heavy metals or dioxins. For questions about specific products and regulations, contact the Minnesota Department of Agriculture, Pesticide and Fertilizer Management Division, 651-201-6560.

• Ensure that fertilizers and other potentially hazardous products (e.g., pesticides, household disinfectants) are stored in safe places where children do not have access to them.
• If you are concerned about a possible lead exposure from a product, contact your health care provider for guidance regarding how to obtain a blood lead test.

MDH has recommended that the MDA continue testing and screening products of potential concern in Minnesota for arsenic, cadmium, and lead. Fertilizers of potential concern include micronutrient and phosphate fertilizers, and liming materials, with special emphasis on: (a) waste-derived products, and (b) products available to consumers around the home. MDH has also recommended testing of waste-derived fertilizer products for dioxins.

MDH and MDA will continue working together to provide updated information to the public about potential hazards from fertilizer products. In addition, we will share the screening results with other state and federal regulatory agencies (e.g., Minnesota Pollution Control Agency, Consumer Product Safety Commission, US Environmental Protection Agency).

Contacts and resources

For questions about specific fertilizer products and data, contact: Paul McNelly, Minnesota Department of Agriculture, 651-201-6560.

For questions about potential health risks from fertilizers, see our Contact Health Risk Assessment information.