Why regulators say a '500 fold' increase in pesticide residue is safe

When Australian regulators were tasked with assessing the safety of Syngenta's new pesticide isocycloseram in 2021, they were the first in the world to do so.

"At this stage, there are no approvals for this active constituent, or any product registrations anywhere in the world," the Australian Pesticides and Veterinary Medicines Authority (APVMA) public release summary read.

The APVMA is now proposing to raise how much of the chemical residue is legally allowed on berries sold in Australia, angering anti-pesticide campaigners.

Opponents argue the 500-fold increase of the so-called "forever chemical" poses too great a risk to human health.

But the APVMA and Food Standards Australia New Zealand (FSANZ) were satisfied treated berries were "safe for all consumers".

Amid the outrage spreading online, the APVMA said it would consider public comment made in response to the proposal before deciding to proceed.

Setting the safe-to-eat standard

As part of the approval process to use a new chemical on crops, regulators set a maximum residue level or MRL, which is the highest amount of the chemical can legally remain on food sold to consumers.

That determines how much of the chemical farmers can apply, when they can use it, and which crops its allowed on, and how the fruit or vegetable must be treated before it goes to market.

In a statement, a spokesperson for the APVMA said MRLs were not the same as how much can be safely ingested daily over a lifetime without risk to health.

"True safety limits are called Acceptable Daily Intake (ADI) or Acute Reference Dose (ARfD)," the spokesperson said.

"MRLs are set far, far below these health limits.

"Exposure in the real world would be hundreds or thousands of times lower than what is assumed for the sake of assessment under worst case scenarios."

But Josh Davis, the executive director of lobby group Pesticide Action Australia, is not convinced.

The group campaigns to reduce pesticide use, and Mr Davis said isocycloseram was one of several pesticides considered to be PFAS chemicals.

"That means it's a forever chemical," Mr Davis said.

"It's berries in the headlines at the moment, but this speaks to a bigger problem.

"The impact on the environment … the health impact in rural communities, then it also moves into the food chain and eventually onto consumers."

In a statement, Syngenta said its isocycloseram-based products had been rigorously assessed and approved by the APVMA.

"[They] have determined that they are safe and effective when used according to the permit conditions or label,"

it said.

Pitched as a solution to hard-to-manage pests, such as thrips and mites, isocycloseram was originally approved for use in a variety of vegetable crops before being expanded to include tree crops, such as citrus and almonds, and eventually berries.

The chemical is not approved for use in Europe, which is implementing broad bans on what it defines as PFAS chemicals, though not all regulators agree isocycloseram falls into that category.

When the United States Environmental Protection Agency (EPA) approved the registration of the pesticide in November 2025, it did not classify it as PFAS.

"This new active ingredient will give farmers an additional tool to help manage crops and grow more food for our country," the agency said.

"Some of the target pests for these products can cause significant crop damage and financial loss to growers."

In January, US conservation groups filed a lawsuit challenging the approval, which they said ignored evidence of health impacts in animal studies.

"We’re going to fight like hell to make sure these forever pesticides aren't allowed to poison our grandchildren's grandchildren," Nathan Donley from the Center for Biological Diversity said in a statement.

Confidence in consumption

In Australia, horticulture groups have been tight-lipped about the proposal.

A spokesperson for AusVeg, the national peak industry group representing vegetable, potato and onion growers, referred questions to the APVMA and agricultural chemical industry group CropLife, which did not respond.

Grower group Berries Australia declined to comment.

The APVMA spokesperson said it was misleading to reference a single level increase, such as "500-fold,"  because it did not reflect the "many layers" of safety margins Australian regulation sat within.

"Before an agricultural chemical can be approved for use, companies must submit an extensive package of data from toxicity studies,"

the spokesperson said.

"These studies test a wide range of doses, from very low to extremely high, so it’s possible to identify the point at which harmful effects begin to occur.

"To inform APVMA's initial registration decision on isocycloseram, a complete high-quality data package was supplied that met international standards."

But Mr Davis said the process should include independent scientists reviewing the chemicals before they are approved for use.

"It's put into the Australian market first and we don't want Australian consumers to be the human experiments for this,"

he said.

"Other countries, like within the UK and EU ... haven't approved this.

"They're taking what's called the precautionary principle, which is putting health and environment first and giving us the benefit of the doubt."

ABC Rural Weekday News

ABC Rural Weekly News

Email address