A range of tropical fruit including mangoes and avocados are now no longer allowed to be dipped in dimethoate, a neurotoxin banned in Europe but still used in some countries as an insecticide.
This week Australia’s chemical regulator, the Australian Pesticides and Veterinary Medicines Authority (APVMA), issued a 12-month suspension notice after testing found dimethoate residue above the maximum permissible limit on the skin of mango and avocado samples.
The announcement said the use of dimethoate as a post-harvest dip to control fruit fly on avocados, mangoes and other tropical fruits like bananas, custard apples, feijoas, guavas, lychees and pawpaw “may not meet the safety criteria”.
The APVMA says the residual insecticide levels detected “are unlikely to pose a significant risk to human health”, but issued the suspension as a precaution.
Some in the horticulture industry say the move could affect supplies of fruit and impact the price and availability in southern states.
Dimethoate and its breakdown product omethoate are insecticides from a group of chemical substances known as organophosphates.
In Australia, it’s been used to control more than 80 insect pests in horticultural and agricultural production since 1956.
In the case of mangoes and avocados, the fruit is either dipped in or sprayed with the insecticide to control Queensland fruit fly, a native pest found throughout eastern Australia.
There are more than 150 species of native fruit fly in Australia but most don’t attack commercial crops.
The suspension only relates to use of dimethoate as “a post-harvest dip for tropical and sub-tropical fruit with inedible peel”.
Dimethoate products are still licensed for use until the point of harvest, which includes applying it to crops via a spray.
Since 2004, dimethoate has been under review by the APVMA and, in 2011, its use was banned on a number of products including stone fruit, grapes, figs, guavas and strawberries, and was no longer available for home gardeners.
Dimethoate has a toxic effect on the nervous systems of fruit fly and other insects such as ticks and mites.
The problem is, dimethoate is also toxic to the human nervous system, albeit if ingested at much higher doses.
Until now the APVMA has managed the risk to human health by regulating the maximum residue level (MRL) of the chemical on the skin of fruit.
“Unfortunately, in this last season, levels have been detected which have been above that maximum level in both avocados and mangoes that have been treated post harvest with dimethoate,” APVMA executive director Sheila Logan told the ABC’s Matt Brann in August.
“With the levels we’ve detected on the last season, consumption at that level is unlikely to pose a significant risk to human health.”But it’s about the established acceptable levels, and so it’s eating into what we’d call the safety factors.”
The MRL is the highest amount of a chemical residue allowed in a food product.
In Australia, state and territory food regulatory agencies monitor and enforce the Food Standards Code, including MRLs.
The agencies undertake surveillance programs for chemical residues in food and also monitor how chemicals are used by food producers.
The Australian Mango Industry Association (AMIA) has raised concerns that the suspension on dipping fruit in dimethoate could restrict the transport of fruit into states like Western Australia and result in an oversupply in other states.
Other fruit growers in Queensland say that while dimethoate is not preferred, it’s an effective back-up pest control.
There are a number of alternatives to dimethoate, such as fumigation and irradiation, but some of these pest deterrents also carry risks to human health and the environment.
