Methyl bromide, also known as bromomethane, is an organobromine compound with the chemical formula CH3Br. This gas is colorless at room temperature, whereas it is a liquid at 38.5 degrees Fahrenheit or below it.

Methyl bromide is usually transported in its liquid state. In the gas state, the gas is odorless, colorless, and non-flammable in low concentration, whereas it has a musty or fruity odor in high concentration.

Methyl bromide is considered three times heavier than air, with a density of 3.97 kg/m3 at 0 degrees celsius. Its melting point is -93.66 degrees Celsius while its boiling point is 4 degrees celsius. It has a tetrahedral shape.

Bromo methane is produced both industrially and biologically. Both natural and human resources are accountable for making bromomethane. Marine organisms alone have fifty-six tonnes of methyl bromide annually in the ocean.

A family of Brassicaceae, terrestrial plants produces methyl bromide in smaller quantities. It is often made in the industries by treating methanol with bromine in sulfur or hydrogen sulfide. 

The following reaction is performed to produce bromomethane in more significant quantities:

 6 CH3OH + 3 Br2 + S → 6 CH3Br + 2 H2O + H2SO4 

Why is Methyl Bromide used so excessively?

structure - methyl bromide
Molecular structure of Methyl Bromide (source)

The marine organism produces this compound in tonnes, which comes in handy and does not require the process to be usable.

The properties of methyl bromide make it a very effective fumigant. Its property to penetrate quickly and deeply into materials at atmospheric temperatures is one of the best advantages over another fumigant. 

Is Methyl Bromide Dangerous? 

Methyl bromide is a toxic substance. Its effects are so dangerous that it is named a neurotoxicant. Extreme exposure to a high concentration of methyl bromide can cause respiratory, cardiovascular, reproductive, and developmental toxicities in humans and animals.

The most common consequences of exposure to methyl bromide are nervous system symptoms such as headache, dizziness, vomiting, blurred vision, etc. Prolonged exposure to methyl bromide can lead up to fatal death.

Although the effects of methyl bromide may not be seen within twenty-four hours, it could cause the untimely death of anyone exposed to the gas. It profusely affects the kidney, eyes, liver, and skin.

Transporting Methyl Bromide in a liquid state

The use of bromomethane as a pesticide is plummeting under the Montreal protocol as the gas is responsible for ozone layer depletion. 

Methyl bromide is used in fumigation. Fumigation is a process to control pests, removing harmful microorganisms by filling an area with gaseous pesticides.

Before the crops are planted in a land, farmers inject methane bromide two feet into the ground to sterilize the soil. Immediately after the treatment, the earth is covered by plastic tarps to prevent gas escape to the atmosphere, although up to 90 percent of gas manages to escape to the environment. 

Methyl Bromide for Agriculture

Alternative for BromoMethyl. Copyright: Ag Science TV

Generally, the molecules from the gas are stable in the troposphere; however, under intense ultraviolet light in the stratosphere, they break down and release chlorine or bromine atoms.

Chlorine or bromine, when it comes in contact with the ozone layer, it destroys the ozone molecules. One chlorine atom can consume up to 100,000 ozone molecules before being removed from the stratosphere.

Montreal Protocol 

A few decades ago, when the use of ozone-depleting substances was escalating, it concerned the international community.

The international community, then, formed international cooperation on the issue. The association signed the Montreal Protocol on substances that deplete the ozone layer in 1987.

Even after the protocol was signed, no sign of improvement was seen. Resulting in 1992, the protocol parties decided to alter the terms of the agreement to end production of halons by 1994 CFCs 1996 in developed countries.

The efforts made by the Montreal protocol are evident. Because of the actions made by the Montreal Protocol, the ozone layer is expected to heal itself somewhere within the 21st century fully.

Amendments to Montreal protocol

  1. The London amendment: the amendment was signed in 1990. This amendment required the complete phaseout of CFCs, halons, and carbon tetrachloride in developed countries by 2000 and in developing countries by 2010. Methyl chloroform included in the list of ozone-depleting substances to phase out by the developed countries by 2005 and developing countries by 2015
  2. The Copenhagen amendment: signed in 1992; this amendment required the complete phaseout of ODS by 1996 in developed countries.
  3. The Montreal amendment: signed in 1997; this amendment required a complete stop use of methyl bromide in developed countries by 2005 and developing countries by 2015, respectively. 

The following amendments, the Beijing amendment in 1999 and the Kigali amendment in 2016, mandate similar rules to phase out ozone-depleting substances. 

Methyl Bromide and ozone layer depletion

ozone depletion - methyl bromide
Ozone layer depletion contributor as of Montreal protocol and how ozone healed after that (source)

Overuse of methyl bromide could cause severe permanent damage to the ozone layer. The effects when the ozone layer is depleted are discussed below. 

If the ozone layer is depleted, there will be an abrupt rise in the earth’s temperature because the UV radiation does not get blocked by any layer in the atmosphere other than the ozone layer.

And we are well acquainted with the ramifications of global warming. The UV rays will directly enter the earth’s surface without any hindrance.

When UV radiation comes into contact with humans, it causes severe damage. Exposure to UV rays causes premature aging of the sun. It also causes damage to eyes such as cataracts, pterygium, burned cornea, etc.

Weakening the immune system so that the body has a hard time fighting the diseases is also a significant problem caused by exposure to UV rays. 

Are there alternatives to Methyl Bromide?

Regular methyl bromide users have already replaced many alternatives to methyl bromide and many. The viable options include cultural practices such as crop rotation, cover crops, plant breeding, grafting organic amendments, biological controls, various alternative chemicals such as chloropicrin, metam sodium, methyl isocyanate, and physical control methods like steam treatments, solarization, and biofumigation. 

Complete Phase-Out of Methyl Bromide and its Barriers 

trend - methyl bromide
Methyl Bromide trend in West Asia (source)

Costa Rica became the first Central American country to end the use of methyl bromide. Eliminating methyl bromide was one of the measures adopted by the government according to the Montreal Protocol that Costa Rica ratified in 1991.

Due to global efforts to ban methyl bromide, the environment is better day after day. The environmental achievements are already evident, with the ozone layer starting to heal itself. 

Although we have come to the point of almost no use of methyl bromide, many nations were reluctant to ban out the use of methyl bromide.

A survey made responded with three concerns about the phaseout among many countries, and they were:

  1. Quarantine and pre-shipment (QPS) requirements of importing countries,
  2. Afraid of potential economic loss. If it happens, then it’s all downhill for that country. Many industries at that time built for fumigation could collapse with that one decision of the legislature, 
  3. Lack of coordination from the government agencies. Many agencies could not support such an agreement because it could affect the country in various ways.

Wrapping up

Methyl bromide has many advantages for fumigation purposes. Commonly used for pest controls, this chemical provides an edge on agricultural yields.

Though, the detrimental effect of this chemical cannot be unseen. Thus, banning the chemical is an optimal decision to save the earth. 

Phasing out methyl bromide, including other ozone layer depletion substances, seemed to be very beneficial. Once created by the overuse of such chemicals, the ozone holes heal themselves.

Many research shows that the ozone layer could get back to its pristine form if we continue to phase out the ozone-depleting substances. 

Many organizations are already preaching about the benefits of banning methyl bromide; We must say too. From an individual standpoint, a little effort can significantly impact this world.

Banning this harmful compound while cultivating and taking some other way to control pests are the methods the world needs to learn.

Reusing plastics or not using plastics can help protect the earth. Ban ozone-depleting substances, save the planet.

Not only bromomethyl but there is also another chemical threatening our existence. Check out our article on the hazards of Formaldehyde HERE.

(Last Updated on December 3, 2021 by Sadrish Dabadi)

Saurav Khadka, with his A levels in computer science from Saipal Academy, owns a keen desire to know more about the environment. He wants to preach his knowledge to others by learning through his hobbies; reading, writing, traveling, and watching movies. He believes sharing his insight regarding a sustainable environment will undoubtedly generate positive perceptions in the people.