Conventional Fumigants

Most quarantine and stored-product fumigation still relies on a small group of chemicals developed decades ago. Each carries serious risks to workers, the environment or long-term effectiveness. Regulators are tightening the rules on all of them.

Methyl bromide

  • The most potent ozone-depleting substance still in use (APVMA).
  • Phased out for most uses under the Montreal Protocol. Quarantine and pre-shipment use is still exempt, at around 10,000 tonnes a year over the last decade (Ozone Secretariat).
  • More than 85 per cent of the methyl bromide used is vented directly to the atmosphere after treatment (Ozone Secretariat).
  • Highly toxic and difficult to smell. Exposure can cause headaches, dizziness, nausea, blurred vision and convulsions. High concentrations can be fatal. Long-term exposure can cause loss of muscle function and memory impairment (SafeWork NSW).
  • A proposed cut to the worker exposure limit in Australia from 5 ppm to 1 ppm is expected to significantly reduce its use (Ozone Secretariat).

Phosphine

  • A highly toxic gas. In the lungs it forms an acid. Large exposures can damage the kidneys, liver and heart, cause fluid on the lungs and convulsions, or cause death (WorkSafe Queensland).
  • Long-term repeated exposure may cause anaemia, bronchitis, speech and motor disturbances, and spontaneous fractures (WorkSafe Queensland).
  • Work health and safety ministers agreed to cut the eight-hour exposure limit from 0.3 ppm to 0.05 ppm. In Western Australia the new limit takes effect from 1 December 2029 (WA Government).
  • Pests are becoming resistant. Strong resistance in stored grain insects has increased over the past decade. Resistance has now spread to grain growing regions in all states (GRDC).

Sulfuryl fluoride

  • Widely adopted as a methyl bromide replacement. It does not deplete ozone, but it is a potent greenhouse gas.
  • About 4,800 times more potent than carbon dioxide at trapping heat. It stays in the atmosphere for about 36 years (Scripps Institution of Oceanography).
  • Global emissions rose from 0.5 to 2.9 thousand tonnes a year between 1978 and 2019. Growth is driven by structural fumigation and post-harvest treatment of grains (NASA Airborne Science).

Hydrogen cyanide

  • Among the most rapidly acting of all known poisons. Even small concentrations are extremely hazardous (Safe Work Australia).
  • It enters the body through the lungs or skin. It stops the body using oxygen. Severe poisoning can lead to cardiac arrest and death (Safe Work Australia).

A lesson from ethylene dibromide

Ethylene dibromide was once a common grain and soil fumigant. The US EPA banned those uses in 1984 and classifies it as a probable human carcinogen (US EPA). Fumigants that seemed indispensable can be withdrawn once their risks are understood.

The practical burden

  • Each container must be fumigated within its own exclusion zone.
  • Containers need an extended venting period before they can be opened.
  • Residues remain a risk on arrival. Studies have found methyl bromide above its occupational exposure limit in up to 21 per cent of containers tested (EU-OSHA).

A safer direction

Australia has begun approving ethyl formate for brown marmorated stink bug treatment. DAFF notes it is not an ozone depleting substance, occurs naturally in some fruits and breaks down quickly in the environment (DAFF). UBL’s patented Fume8 technology was developed to deliver ethyl formate safely on site.