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Multi-attribute Toxicity Factor


Multi-attribute Toxicity Factor

Introduction :

C. Benbrook and other researchers designed the MATF indicator to calculate the toxicity of pesticides for the "Healthy Grown" Wisconsin Potato IPM Labeling Project. That project was a collaborative effort between the University of Wisconsin, the Wisconsin Potato and Vegetable Growers Association, and the World Wildlife Fund. This model calculates toxicity factor values for acute mammalian risk, chronic mammalian risk, ecological impacts, and impacts on beneficial organisms.

Reference:

  • Benbrook, C., Sexon, D., Wyman, J., Stevenson, W., Lynch, S., Wallendal, J., Diercks, S., Van Haren, R., Granadino, C. 2002. Developing a pesticide risk assessment tool to monitor progress in reducing reliance on high-risk pesticides. American Journal of Potato Research 79, 183-199.


Equations :

  1. Acute Mammal Toxicity Value = 1/Rat Oral LD50 *500
  2. Chronic Mammal Toxicity Value = ((0.1/RFD)*ED)+Q*50*Cancer class)
  3. Ecological Toxicity Value = LC50 Daphnia + LC50 Trout + LC50 Bluegill
  4. Beneficial Toxicity Value =
    (Resistance Score + Beneficial Impact Score +Bee Toxicity Score)*.05
  5. Toxicity Factor = [(0.5*AM) + CM + ECO Index + (1.5*BiolPM Index)]*[application rate]

In equation (1) the toxicity value is obtained by taking the inverse of the Rat Oral LD50 value and then multiplying by a MATF designed scaling factor of 500. In equation (2), the chronic mammal toxicity value is obtained by manipulating ranking scores for endocrine disruption (ED) and cancer class. In addition, the cancer potency factor (Q*) is also used in equation (2). For equation (4) a group of expert opinion is used to place a value on the various variables. The resistance score reflects the pesticide's likelihood of causing resistance in target pests in Wisconsin, the beneficial impact score reflects the pesticide's potential impact on non-target organisms in Wisconsin, and the bee toxicity score reflects the pesticide's potential impact on bees. All scores in equation (4) were devised by a team of experts and included in the MATF reference material. Final values from equations (1-4) are capped at 200.

Ranking Scheme :

  • Endocrine Disruptor
    3 = yes
    1 = no information
  • EPA Oncogenicity Classification
    10 = Class A or B2
    5 = Class C
    2 = Class D

List of Symbols :

Symbol
Description
AM acute mammalian toxicity value
Application Rate amount of pesticide a.i. applied (lbs/acre)
BiolPM Index impacts on beneficials and IPM systems
CM chronic mammalian toxicity
ECO Index ecological impacts
ED Endocrine Disruptor Classification
Q* EPA oncogenic potency factor (slope of the dose-response curve)
RfD EPA Chronic Reference Dose


Analysis :

This model was specifically designed for Wisconsin potatoes. As a result, using this indicator on other crops and in other regions may result in inaccurate predictions of risk. However, by adjusting the weighting factors in this system's equations could result in suitable results for differing environmental regions and crops. This model also relies on values for beneficial organisms determined by experts. These values only apply to Wisconsin. Therefore, for the BioIPM index to have any meaning, these values will have to be adjusted when using this model in new regions or with new crops. Individuals using this system should also be cognizant of the fact that Q* values and endocrine disruptor values can be difficult to obtain.

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