Olympia, Wash. — Results of a special analysis conducted on 35 samples of fertilizer are available for review, but still to come is a clear understanding of what the data means from the standpoint of human health. The analysis was conducted in response to public questions and concerns about the use of industrial by-products as fertilizers and soil additives.
Thirty-five samples of a variety of fertilizers were collected by the Washington State Department of Agriculture and analyzed at the Department of Ecology’s Manchester Laboratory. The results are being reviewed by soil scientists from Washington State University’s Puyallyup Research and Extension Center and by toxicologists at the Washington State Department of Health. These samples represent an initial screening of a limited number of fertilizer products in the state, and the results do not provide information on the variations of metals concentrations within products.
“So far, the levels of toxic metals in the majority of the fertilizers tested are well below the limits set for land application of biosolids,” said Greg Sorlie, Ecology’s program manager for the hazardous waste and toxics reduction program. Biosolids is another name for sewage sludge that is used as fertilizer.
The U.S. Environmental Protection Agency (EPA) set two standards for biosolids. The standard referred to above, concerns the total amount of metals that can be applied to agricultural land. The other standard is a maximum allowable concentration of metals, or ceiling limit, in the biosolids. Compared to this latter standard, lead, arsenic and cadmium were found in concentrations higher than the biosolids standard in several products.
Biosolid standards have only been developed for nine toxic metals: arsenic, cadmium, copper, lead, mercury, molybdenum, nickel, selenium and zinc.
“We believe that comparing the fertilizer samples to the biosolids standards is a good place to start in determining if fertilizers contain levels of metals that may cause concern,” Sorlie said. “Although we have not fully analyzed the data, we promised concerned citizens to make the data available as soon as we had them. Meanwhile we are moving ahead to get a full understanding of the significance of what we’ve found.”
One unresolved question about comparing fertilizer products to biosolids is that the forms of the metals in biosolids may be taken up by plants differently than the forms of metals found in fertilizer product. Because of this, the biosolids standards may underestimate the plant uptake of metals from fertilizers and therefore may not be adequately protective.
“While we look at the concentrations of metals, we’ll be trying to learn their significance to public health, plant uptake, plant productivity, and soil degradation,” Sorlie said. “We are committed to learning everything we need to know about these products to make sure that public health is protected.”
The state departments of Ecology and Agriculture plan to propose legislation to the governor and state legislators which will strengthen the review process for products applied to farm land.
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This is a joint news release. For further information you can contact:
Jani Gilbert, Department of Ecology, (509) 456-4464
Gary Perkins, Department of Agriculture, (360) 902-1813
Linda Waring, Department of Health, (360) 753-3237
Shiou Kuo, Washington State University, (253) 445-4573