Standards for Maximum Allowable Levels of Metals in Fertilizer

The Fertilizer Regulation Act of 1998 included standards for the maximum acceptable annual addition of metals to soils. The Washington Standards for Metals set a maximum allowable yearly addition of nine metals to Washington soils. These are listed below.

The Nine Metals of Concern

Generally, waste-derived and micronutrient fertilizers must be tested for levels of soluble metals using the Toxicity Characteristic Leaching Procedure (TCLP) metals analysis and for halogenated organic compounds.

Washington State Department of Agriculture Fertilizer Database contains all the test results that are submitted to Ecology.

Then, the Washington State Standards for Metals are used to assess if the fertilizer is eligible for registration. To assess if a fertilizer is likely to pass review:

  1. Analyze the fertilizer to determine the amount of each of the nine metals of concern in the fertilizer product, and

  2. Calculate the amount of metal that would be added to the soil by using the fertilizer at the maximum application rate for that product.

The total amount of restricted metals that would be added to the soil is estimated by multiplying maximum application rate (usually taken directly from the product label) by the amount of each metal in a fertilizer.

To be registered in Washington, that maximum application rate may not exceed the maximum allowable level for that metal, as defined in the Washington Standards for Metals. The chart below lists the maximum allowable levels for metals in waste-derived fertilizers. Those in bold have limits defined in the Washington State Standards for Metals at WAC 16-200-7064 (Table 2) of the Washington State Department of Agriculture (WSDA) regulations.

Maximum Allowable Metals Standards

Metal

Maximum Allowable Concentrations by Toxicity Characteristic Leaching Procedure (in ppm)

Washington Standards for Metals Maximum Allowable Levels per year (in pounds per acre)

Arsenic (As)

5.0

.297

Barium (Ba)

100.0

--

Cadmium (Cd)

1.0

.079

Chromium (Cr)

5.0

--

Cobalt (Co)

--

.594

Lead (Pb)

5.0

1.981

Mercury (Hg)

0.2

.019

Molybdenum (Mo)

--

.079

Nickel (Ni)

--

.713

Selenium (Se)

1.0

.055

Silver (Ag)

5.0

--

Zinc (Zn)

--

7.329

The maximum allowable level for halogenated organic compounds is 1%.

Washington’s Fertilizer Regulation Act states that the Washington Standards may be amended if risk-based standards are developed or if scientific studies show that the Washington Standards are not at the appropriate level to protect human health or the environment.

Beginning with the July 1998 registration cycle, the WSDA has applied the Washington Standards for Metals to all fertilizer applications for registration in the annual registration process. The WSDA Database compiles the results of that registration process for each fertilizer product registered for distribution or sale in the state of Washington

Example

The metals analysis for Lovely Lawn Weed and Feed indicates this product contains 5 parts per million cadmium. The label on Lovely Lawn Weed and Feed states that this product should be applied at a rate of 1 lb./250 sq. ft. and at a maximum of three applications per year. This calculates out to be 0.0026 pounds of cadmium/acre/year compared to a maximum allowable level of 0.079 pounds/acre/year for cadmium. Lovely Lawn Weed and Feed is well under the maximum allowable level for cadmium set by the Washington Standards for Metals.

Related information

The Washington State Department of Agriculture (WSDA)

Metals in Fertilizers at WSDA

Fertilizer Product Registration at WSDA