The Australian Pesticides and Veterinary Medicines Authority (APVMA) has 19 active chemical reviews, some dating from 1996.

The agency denies it is not acting fast enough but from July 1, it will be forced to complete reviews within a maximum of five years.

A chemical exposure expert at the National Centre for Epidemiology and Population Health at the Australian National University, Liz Hanna, said the agency was not prioritising Australians' health, which had potentially harmful consequences.

''In the course of 15 years, a considerable body of research comes out to identify the risks of exposure and they would have to totally rewrite the thing multiple times and that is ineffective and inefficient,'' Dr Hanna said.

''We certainly support bringing it down to an upper limit of five years, and ideally we would like for them to have sufficient resources to do a very thorough review in something like two years.''

The authority launched a review into the broad-spectrum insecticide, Diazinon, in 1996, which is still ongoing.

The authority refused to provide information about the average length of reviews and the longest ongoing review. But the review into insecticide azinphos-methyl has been ongoing since the Preliminary Review Findings Report was published in 2006.

The chlorpyrifos insecticide interim report was handed down in 2000, and the preliminary findings were published in 2009. The agency said it expected to finalise the review in 2015.

APVMA pesticides program executive director Raj Bhula said the new laws would allow a maximum of 12 months an assessment, and large reviews would require up to five.

She said the changes to timelines were about providing transparency, and risks found during assessments would be addressed immediately.

''We can make an interim environment decision or suspension … we take suspension actions at various points before we finish a whole review of a chemical,'' Dr Bhula said.

But Dr Hanna said it was nonsensical for the agency to take more than a decade to make findings.

''They don't do their own testing,'' she said. ''If they were a laboratory, you might understand it would take many, many years but what they are essentially doing is a literature review. From a public health perspective, we would regard 15 years as irresponsible.''

Dr Hanna said the authority's refusal to follow European research was baffling.

''We find it amazing when the argument is put forward by the APVMA that they do best practice and they are scientifically evidenced-based, yet when other countries withdraw and ban products and diminish their level of concentration … we don't do that.

''If the findings of the EU find there is human harm with exposure, then our physiology is the same, exposure can be different if it's used on a different crop, but the important thing is that we don't have the flow of run-off like the rainfall that Canada or Europe have, so things can be flushed out of the river systems.

''We don't have any of that so in many respects, our use is more risky because we don't have an ecology that flushes out quickly because we have such little rainfall.''