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What Is Reproductive Toxicity Descriptor ED10 and How to Calculate It?

Little Pro on 2019-08-07 Views:  Update:2019-08-07

ED10 is a very important reproductive toxicity dose descriptor. It is used to describe the potency of a potential reproductive toxicant. In this article, we will explain what ED10 is and show you how to calculate ED10.

What Is ED10?

The ED10 value is the lowest dose which induces reproductive toxic effects with an incidence or magnitude of 10% effect level above background data. It usually needs to be calculated from animal developmental and/or reproductive toxicity studies. 

How Is ED10 Used?

ED10 is primarily used to characterize the potency of a reproductive toxicant (high, medium or low). Each final potency group can be assigned with a generic concentration limit (GCL) or a specific concentration limit (SCL).

  • High potency: ED10 value ≤ 4 mg/kg bw/day
  • Medium potency: 4 mg/kg bw/day < ED10 value < 400 mg/kg bw/day
  • Low potency: ED10 value > 400 mg/kg bw/day

ECHA recommends setting the following GCLs and SCLs for the different categories of reproductive toxicant based on their potency. 

ED10 Reproductive Toxicity

Note: The ED10 is usually in the same range as the NOAEL and LOAEL. Sometimes, the LOAEL can be lower than ED10. If a substance would fall into a lower potency group based on the ED10 but into a higher potency group based on the LOAEL then the higher potency group should be assigned to that substance.

How to Calculate ED10

Let's assume that we have conducted a reliable prenatal developmental toxicity study for substance A and have obtained the following data. 

Type of Study - Effects NOAEL in ppm (mg/kg bw/d) LOAEL in ppm (mg/kg bw/d)

OECD 414, Wistar rats (gavage)

Dose: 0, 20, 60, 180 mg/kg bw

180 mg/kg bw: Postimplantation loss: 35%, reduced fetus body weight by 10%.

60 mg/kg bw: Postimplantation loss: 12% (not statistically significant compared to control data, less than 5%)

20 mg/kg bw: Postimplantation loss: 11%

0 mg/kg bw: Postimplantation loss: 10%

  60  180

Since control postimplantation loss is 10%, ED10 rate would be 20% (10% above control data). Interpolation between NOAEL (classification) (12% at 60 mg/kg) and LOAEL (classification) (35% at 180 mg/kg) can be done using the following equation.

  • Step 1: Calculating steepness  = (180 - 60) / (35 - 12) = 5.22 mg/kg bw/percent
  • Step 2: Interpolation ED10 = steepness x (20-12) + 60 = 102 mg/kg bw/d

This ED10 value of 102 mg/kg bw/d will place substance A into medium potency group.

Reference

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 Tags: Topics - CRAToxicology and Health Risk Assessment

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