Emisiones contaminantes

Situations involving the use of agrochemicals that would require emergency responses could result either from natural causes or human failure. Natural causes include the flooding of stores or the effects of temperature on agrochemicals. Safe storage has been dealt with earlier.

Overheating of agrochemicals could have serious consequences. Agrochemical users should take adequate steps to prevent such occurrences.

Fire is a more serious situation that the user has to deal with, or for which outside assistance must be sought. Again, while the first step is prevention, the user should know what to do in the case of a fire. This section deals with some basic principles of emergency response.

3.5.1. Effects of temperature on

agrochemicals

Agrochemicals are stable at normal temperatures. Extremes of heat or cold may, however, cause deterioration of the container and its contents. This could result in the container leaking or bursting, and consequent spillages. If two or more containers begin to leak different agrochemicals simultaneously, these substances may react and produce gaseous vapours or even heat and fire. In addition, the contents of an apparently sound container may decompose owing to the effect of temperature so that they are no longer suitable for their original purpose. Climatic conditions such as high humidity and direct sunlight may speed up the rate of damage. Agrochemicals should be stored in a manner so as to avoid their being affected by fluctuations of temperature.

3.5.2. Fire prevention and fire-fighting

All possible measures should be taken to avoid fires involving agrochemicals. These will include:

– banning smoking or the use of naked flames where agrochemicals are stored or used;

– keeping flammable products away from heat sources such as direct sunlight;

– keeping glass containers out of direct sunlight as they could act as magnifying glasses and focus the sun's rays on flammable material to cause a fire;

– arranging the storage area so that it does not adjoin other sites with a risk of fire such as those storing hay, straw or petroleum fuel;

– avoiding the cause of a fire from an unsafe electrical installation or sparks from nearby welding or grinding activities;

– having a pre-arranged fire-fighting plan with ready access to a source of water and other extinguishing equipment to deal with emergencies.

In the event of fire:

– do not put lives at risk. Get everyone except fire- fighters away from the site and beyond the line of smoke and chemical discharge;

– call for help if needed, including the firefighting services if the fire cannot be extinguished with available equipment;

– inform fire-fighters and other helpers about any agrochemical which may react dangerously such as those which are flammable, toxic or in pressurised containers;

– attempt to contain the fire and any run-off from agrochemicals or water so that the wider environment is not contaminated;

– after extinguishing the fire, clean up appropriate protective clothing and dispose safely of all damaged or contaminated material to avoid exposing others to agrochemical risk.

3.5.2.1. Emission of toxic gases

The extent of toxic gas emission from an agrochemical fire is proportional to the number and type of the products involved. In practice, however, it is always best to assume that an agrochemical fire will produce toxic gases, which may be lethal, from burning chemicals or plastic containers. There are also particular circumstances such as fires involving non-toxic fertilisers which give off toxic fumes when exposed to fire. Ammonium nitrate is one such example. Fire-fighters should take necessary precautions for fighting fires where toxic gases are released. They should position themselves on the windward side and use self-contained breathing apparatus.

3.5.2.2. Choice of fire-extinguishing agents

The type of extinguishing agent must be the most appropriate (table 1). It must be safe and not react dangerously with flammable materials or conduct electricity.

Most fires develop slowly. A bucket of sand or a portable fire extinguisher may be all that is initially needed. Larger fires should be fought by professional fire- fighters.

Table 1. Which fire-extinguishing agent to use

Class of fire Water Carbon Dry chemical

Dioxide gas powder

A Paper 9 – 9 Wood 9 – 9 Textile 9 – 9 Fabric 9 – 9 B Flammable liquids – 9 9 C Flammable gases – 9 9 Electrical hazards – 9 9

The agrochemical user should be prepared by having portable extinguishers at the storage site and being trained to use them. Fire extinguishers should be of an adequate size and positioned where they will be readily available.

Table 2. Action of fire-extinguishing agents

Table 2 lists the different types of fire-extinguishing agents and their uses. The most suitable portable extinguisher for an agrochemical fire is the dry chemical type. It is effective against fires involving combustible flammable liquids and gases. There are, however, other

extinguishers which, according to circumstances, may also be suitable.

Fighting large agrochemical fires with water alone has been successful, but there are disadvantages. The first is that water used on a fire may wash out poisonous material to contaminate the wider environment. Bunding or the construction of a small earth wall around the store will help to prevent this by containing the polluted water. This should be an essential feature of all larger stores. The second disadvantage concerns those agrochemicals which react with water to produce poisonous gases. However, most agrochemicals are compatible with water, the exceptions are some cyanide compounds and phosphide. These substances, which are extremely toxic gases used as fumigants, release hydrogen cyanide gas and phosphine respectively in contact with water.

Discussion and activities

Type How fire-extinguishing agents put out fires

Best for

Water Mainly by cooling burning material

Class A fires involving solids. Danger – do not use on live electrical appliances or on burning fat or oil

Multi-purpose dry powder

Knocks down flames and, on burning solids, the powder melts to form a “skin“ smothering the fire. Some cooling effects

Class A fires involving solids and Class B fires involving liquids. Safe on live electrical equipment although does not readily penetrate the spaces inside equipment and the fire may flare up again

Standard dry powder

Knocks down flames Class B fires involving liquids. Safe on live electrical equipment although does not readily penetrate the spaces inside equipment and the fire may flare up again AFFF (Aqueous film-forming foam) Forms a fire- extinguishing film on the surface of a burning liquid.

Has a cooling action with a wider extinguishing application than water on solid combustible materials

Class A fires involving solids and Class B fires involving liquids

Carbon dioxide (CO²)

Vaporising liquefied gas which smothers flames by displacing oxygen in the air

Class B fires involving liquids. Clean, effective and safe on live electrical equipment

1. Have you, or anyone in the neighborhood, fallen ill from working with agrochemicals?

1.1 What were the symptoms? 1.2 What was the treatment? 1.3 What were the consequences?

2. Try to remember and list the products that caused these illnesses.

3. Could you list the products to which you would attribute any cases of illness that may have occurred after several years of exposure?

4. Record the name and address of the trained first-aider nearest to your home.

4.1 How often do you consult the first-aider? 4.2 List the instructions you have received from the

first-aider.

4.3 What are the differences, if any, in giving first aid to a person who is: (a) poisoned and unconscious; (b) poisoned but conscious; or (c)

burnt with agrochemicals?

5. Is there a poison information centre in your country? If yes, (a) record the name and address; (b) list ways in which it could help you; (c) draft a telegram for advice assuming that a person in your locality was poisoned with a new pesticide, and the label does not give information about any antidote. Aside from such a centre, do you know anywhere you can seek advice about poisoning?

Point to remember:

Remember always to take the containers of agrochemicals used, along with their labels, if a case of acute poisoning is taken to a hospital, doctor or other health worker Take extreme precautions in transporting the containers. The doctor or other health worker consulted may then read the label and give prompt treatment.

6. Have you ever seen or heard about a fire in an agrochemical store in your locality or any other locality?

6.1 Do you have any fire-fighting equipment? 6.2 Who trained you in its use?

6.3 How often do you inspect it?

6.4 List six steps in attempting to fight a fire in your store.

6.5 Record the name and address of the firefighting authority nearest to your home. 6.6 Prepare a chart to illustrate the different types

of fire-fighting agent you would use for different classes of fire. Describe how different agents act to extinguish a fire.

Point to remember:

Fire extinguishers are very important and should be readily available. You should always be trained on how and when to use the various types of extinguisher.