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Statement of Uniform Interpretation and Policy (SUIP) #25 - The "Heavy Metal Rule"

25. Federal, state and industry sponsored risk-based assessments(1) have been completed and the results demonstrate that metals in fertilizer generally do not pose harm to human health or the environment. Except as otherwise provided below, as a guide(2) for implementation of Section 13(a) of the Uniform State Fertilizer Bill, fertilizers that contain guaranteed amounts of phosphates and/or micronutrients are adulterated when they contain metals in amounts greater than the levels of metals established by the following table:

Metals
ppm per 1% P2O5
ppm per 1% Micronutrient(3)
Arsenic
13
112
Cadmium
10
82
Cobalt
136(6)
2,228(6)
Lead
61
463
Mercury
1
6
Molybdenum
42
300(4)
Nickel
250
1,900
Selenium
26
180
Zinc
420
2,900(4)

To use the table, choose one of the following three situations (A very useful SUIP#25 Calculator is available - it works in Firefox, but not Internet Explorer):

  1. Fertilizers with a phosphate guarantee; but, no micro-nutrient guarantee:
    Multiply the percent guaranteed P2O5 in the product by the values in the table to obtain the maximum allowable concentration of each metal. The minimum value for P2O5 utilized as a multiplier shall be six (6.0).
  2. Fertilizers with one or more micro-nutrient guarantees; but, no phosphate guarantee:
    Multiply the sum of the guaranteed percentages of all micro-nutrients (as defined by AAPFCO's Official Fertilizer Term, T-9) in the product by the value in the appropriate column in the Table to obtain the maximum allowable concentration (ppm) of each metal. The minimum value for micro-nutrients utilized as a multiplier shall be one (1).
  3. Fertilizers with both a phosphate and a micro-nutrient guarantee:
    1. Multiply the guaranteed percent P2O5 by the value in the appropriate column. The minimum value for P2O5 utilized as a multiplier shall be 6.0. Then,
    2. Multiply the sum of the guaranteed percentages of the micro-nutrients by the value in the appropriate column. The minimum value for micro-nutrients utilized as a multiplier shall be one (1). Then,
    3. Utilize the higher of the two resulting values as the maximum allowable concentration (ppm) of each metal.

Biosolids and All Compost Products:
Biosolids, and all compost products(5), shall be adulterated when they exceed the levels of metals permitted by the United States Environmental Protection Agency Code of Federal Regulations, 40 CFR Part 503 Dried biosolids and manure, as well as manipulated manure products either separately or in combination, shall also be deemed adulterated when they exceed the levels of metal permitted by the United States Environmental Protection Agency Code of Federal Regulations, 40 CFR Part 503 (Biosolids). Hazardous waste derived fertilizers (as defined by EPA) shall be adulterated when they exceed the levels of metals permitted by the United States Environmental Protection Agency Code of Federal Regulations, 40 CFR Parts 261, 266 and 268.

Hazardous waste derived fertilizers (as defined by EPA) shall be adulterated when they exceed the levels of metals permitted by the United States Environmental Protection Agency Code of Federal Regulations, 40 CFR Parts 261, 266 and 268.


(1) Woltering, Daniel M. 2004. Health Risk Assessment for Metals in Inorganic Fertilizers: Development and Use in Risk Management. In Environmental Impact of Fertilizer on Soil and Water. Hall, William L. Jr. and Wayne P. Robarge, Editors. American Chemical Society Symposium Series No. 872. p124-147.

(2) These guidelines are not intended to be used to evaluate horticultural growing media claiming nutrients but may be applied to the sources of the nutrients added to the growing media.

(3) Micro-nutrients (also called minor elements) are essential for both plant growth and development and are added to certain fertilizers to improve crop production and/or quality. These micro-nutrients are defined by AAPFCO's Official Fertilizer Term, T-9.

(4) Only applies when not guaranteed.

(5) Includes all compost products separately or in combination with biosolids, manure or manipulated manure, even those registered as fertilizers (making nutrient claims). (Official 2003)

(6) Official 2008.