The one-year dog study in agrochemical testing: time for a global change

For decades, regulations for the toxicity testing of agrochemicals have required the use of dogs as well a rodent species, usually the rat. Testing typically consists of initial exploratory studies at a range of different concentrations to establish the dose which is then used in the short-term (90-days) and long-term (one-year) toxicity tests.  For each new chemical tested this uses at least 70 dogs.  Multiply this by the number of new chemicals tested each year and it quickly becomes thousands of animals.

In recent years there have been changes to the regulatory requirements such that the one-year dog study is no longer required in the EU (Regulation (EC) No 1107/2009), and is only required if the dog is shown to be more sensitive than rodents in the 90 day studies in the US, Canada and Australia.

Nevertheless, countries like Brazil and Japan still require the one-year dog study before a product can be approved and this means that companies conduct the study to enable global marketing, irrespective of the fact it is not required elsewhere.

A recent publication in Critical Reviews in Toxicology focused on one of these key regions, Japan, and demonstrated the redundancy of the one-year dog study for agrochemical testing based on an analysis of data on the 400+ pesticides registered in this region.  A key way of protecting human health is to set limits on the amount of any particular chemical that a human should be exposed to over a lifetime, setting a so-called Acceptable Daily Intake (ADI).  Of the 400 pesticides, 45 have ADIs derived from dog studies and these 45 were analysed in detail.

The study showed that in over 90% of cases, there would be no real difference in the exposure limits set without using data from the one-year dog study. In 6.5% of cases there might be a difference, and in only one case (2.2%) was there a genuine difference in the ADI recommendation.

The retrospective data analysis showed that overall, in 99% of cases there would have been no significant impact on the safe exposure levels that were derived in Japan had the one-year dog study not been conducted, and in all cases consumer exposure would have remained well below the ADI.

This key publication adds substantially to the weight of published literature that now indicates the one-year dog study adds no significant value to the safety assessment of agrochemicals. European regulations no longer require the study to be carried out. We now need to work towards a harmonised approach with countries in other parts of the world. The time has come for the one-year dog study to be removed from test requirements globally.

For further information on the study details, please refer to the paper;

Kobel W, Fegert I, Billington R et al. (2014) Relevance of the 1-year dog study in assessing human health risks for registration of pesticides. An update to include pesticides registered in Japan Critical Reviews in Toxicology 44(10) 842-848 DOI:10.3109/10408444.2014.936550.

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