The information below is an informal summary taken from the reassessment application document and is intended as background to the reassessment.
People are strongly encouraged to read the application document for more detailed information, and to make submissions. Information received in submissions will be presented to the Authority to help inform the decision-making process.
What is methyl bromide?
Methyl bromide is a colourless, odourless, heavier-than-air gas.
What is it used for?
It is used internationally as a fumigant to kill a wide range of pests (including weeds, insects, mites and rodents). It is a hazardous substance and must be used with care.
Does it have a role in biosecurity?
It is an important part of New Zealand’s biosecurity shield. It helps protect our environment and economy by preventing new pest species arriving here in imported goods. Any new pests that slip into New Zealand could have a devastating impact on industries such as forestry and agriculture, as well as on human health.
Methyl bromide is also used in New Zealand to kill pests on timber shipments being sent overseas. Some countries insist on the use of methyl bromide before timber shipments leave our ports. Australia requires us to fumigate capsicums and tomatoes before they can be sent there.
Where is it used?
It is used primarily at ports (in containers, ships’
holds, and onshore stacks of timber/logs under cover),
transitional facilities around the country and
quarantine treatment centres such as Auckland Airport.
What is the history of the use of methyl bromide?
Methyl bromide is a naturally occurring substance. It was first used commercially at the beginning of the twentieth century, primarily as a fire extinguishant, including on ships.
Methyl bromide began to be used as a soil fumigant to control insect pests in the 1930s, as well as to protect stored agricultural produce and other applications. Its use as an insecticide fumigant increased in the 1980s but since then it has been phased out under the Montreal Protocol, an international agreement made in 1987 to restrict the use of ozone-depleting substances.
New Zealand was required to reduce its use of methyl bromide, apart from quarantine and pre-shipment (QPS) use and other “critical use” purposes.
Use as a soil fumigant in the strawberry industry was recognised as a critical use and therefore able to be imported up until 31 December 2007.
Growers who imported methyl bromide prior to 31 December 2007 are still be able to use it to fumigate strawberry beds until their stocks are exhausted.
This is expected to happen by the end of 2010.
What part does it play in the export trade?
In 2008, log exports from New Zealand were worth over $600 million. Pre-shipment fumigation is a requirement of many trading partners who take these logs, for example China, Malaysia and India. The log export trade to China is rapidly increasing and has tripled over the past two years.
How much is used in New Zealand?
In 2007, 170 tonnes were used, primarily (79 percent) for treating timber. In the same year, the USA and China used 1,757 and 1,112 tonnes respectively.
What controls are in place now?
As with many hazardous substances, methyl bromide
needs to be treated with care and used in accordance
with the controls. The current controls are amongst the
toughest on any chemical, and cover its importation,
transport, storage, use and disposal, including:
• a special licence is required to possess it;
• signs must be erected at the site where it is used;
• prior and post-notification of the use of the gas must
be given to appropriate persons and authorities;
• emergency plans must be in place;
• users need to wear protective clothing;
• there are exposure limits set for workers and others;
and
• supplies of methyl bromide must be ‘tracked’.
In addition to the controls applying under the HSNO Act, use of the substance is also regulated under other legislation including the Health and Safety in Employment Act, Agricultural Compounds and Veterinary Medicines Act, Resource Management Act, MFAG Standards.
The agencies involved in enforcement include the Department of Labour, the NZ Police, the Ministry of Health, Maritime New Zealand, the NZ Transport Agency and regional councils.
The Pest Management Association of New Zealand code of practice approved by the Authority in 2008 provides guidance on the control and safe use of fumigants.
There are three existing HSNO approvals for methyl bromide and related products which are the subject of this reassessment. Two of these, HSR001637 and HSR001638, are for soil fumigants (eg in the strawberry industry) and contain a mixture of methyl bromide and chloropicrin. The other, HSR001635, contains only methyl bromide and is used for QPS. The preliminary recommendations made in the reassessment application are to revoke the approvals for the non-QPS uses.
Is there a link between motor neurone disease and methyl bromide?
There have been claims that incidents of motor neurone disease amongst a group of Nelson port workers may have been caused by low-level, regular exposure to methyl bromide, and we examined this possibility closely as part of our reassessment.
The way methyl bromide affects the nervous system is not known. However, we have concluded there are clear indications that, in individuals affected following methyl bromide exposure, the effects are not comparable with those of motor neurone disease.
ERMA New Zealand notes that a review by the local
Medical Officer of Health in 2005 of each of the
individual cases of the disease in and around the Nelson
area did not support the conclusion that they were
related to exposure to methyl bromide, and the apparent
cluster was most likely explained on the basis of
“chance”.
The cause of motor neurone disease is not known.
What levels of exposure to methyl bromide are safe?
Provided that levels are below the proposed 1 hour “tolerable exposure limit” (TEL) at the boundary or any places where members of the public may be present, and that the required workplace exposure standard (WES) for the protection of workers is not exceeded, there should be no harmful human health effects. ERMA New Zealand has proposed TELs to address both acute and chronic exposure.
What is meant by “acute” and “chronic” exposure?
Acute exposure is over a short period of time, up to one day. Chronic exposure is longer, and is a term usually meaning regular (for example, daily) exposure for a prolonged period of weeks/months
A “safe” exposure level only has meaning in relation to the length of time someone is exposed. Concentrations of methyl bromide unlikely to cause adverse effects on human health after 1 hour, 24 hours or 1 year exposures have been estimated on the basis of scientific review (including by overseas regulatory agencies). These values are akin to “safe” exposure limits when they are referring to the relevant exposure period.
What is the concentration of methyl bromide in the surrounding air once released?
This will depend on the type of fumigation, the amount of methyl bromide used and the weather conditions. Monitoring data shows that concentrations of methyl bromide decrease rapidly with distance from the fumigation during ventilation. Under the preliminary recommendations in the reassessment application, companies carrying out fumigations would be required to carry out environmental monitoring to check levels.
Where does the gas go after it is used in ships’ holds or under a tarpaulin?
It is released into the air, although some may remain in and around the logs and be released slowly afterwards.
Is there a lingering “cloud” formed by the gas being released into the air after it is used?
No, in normal conditions of use it disperses rapidly.
Is it a neurotoxin?
Yes, methyl bromide affects the nervous system. The acute toxicity of hazardous substances is graded on a scale from 6.1A to 6.1E, with A being the highest acute category. Methyl bromide is a 6.1B.
Has anyone suffered acute health effects methyl bromide in New Zealand?
There have been instances of individuals being exposed to methyl bromide both in New Zealand and overseas. This can occur, for example, when unsuspecting workers open containers without wearing protective equipment. Such cases in New Zealand have been rare comparative to the wide use of the substance over many years.
Has there been testing for the presence of methyl bromide in port workers or others who may have come into contact with it?
We are aware that at least one fumigator carries out regular (approximately six monthly) blood tests of operational staff for bromide levels. That fumigator has advised that it is rare for the results to exceed the normal range for an unexposed person. It is also not possible to be sure that the source of an unusually high level of bromide was methyl bromide itself, as raised blood levels may result from certain foods being eaten.
What are the other sources of bromide?
Bromide is found naturally in soils and in food, particularly in grains. It is also found naturally in human blood at low levels.
Is methyl bromide produced industrially anywhere in New Zealand?
No. All supplies are imported.
Is there an alternative available?
There is no single alternative fumigant or method of treatment currently available and acceptable to the countries we export to.
Phosphine is being used in some situations, for example on logs in ships’ holds while in transit to China. However, the more extensive use of alternatives such as phosphine depends on further research into its effectiveness and subsequent acceptance by trading partners such as China. If India allowed the use of phosphine for timber treatment, and if China allowed lower rates of methyl bromide fumigation, that could lead to a significant reduction in New Zealand’s use of the chemical.
However alternative substances such as phosphine are also highly hazardous, and it is likely they would also have similar effects if not used correctly. These substances require further evaluation and international acceptance before they could become viable alternatives.
Why is our human health risk assessment not based on air dispersion modelling?
No atmospheric dispersion modelling of potential exposure to bystanders from methyl bromide has been undertaken by ERMA New Zealand for the purposes of assessing risks to human health. We consider that, for most situations, measurements of gas concentrations give an objective measure of the gas concentrations for a particular operation provided the monitoring equipment is performing correctly and is located in a downwind position where people might be exposed. ERMA New Zealand notes that for sites with complicated geography and weather conditions, expert advice (including from air dispersion experts) should be obtained to ensure the most appropriate monitoring locations are selected.
Our overall assessment is that the risks to the health of workers and non-workers nearby are negligible provided the strict controls are complied with.
Is ERMA reassessing other substances?
Yes. Since 2006, ERMA New Zealand has been reassessing a list of 20 hazardous substances that includes industrial chemicals, agricultural chemicals and other pesticides, and making recommendations about changes needed. Submissions from the public and interested parties have been sought as part of the process. The list of 20 includes chemicals such as paraquat, carbaryl, diazonon, anti-fouling paints and 2,4-D. To receive updates, register at reassessments@ermanz.govt.nz
Last Updated Nov 2009