Risk assessment of pesticides and preventive measures
Surveillance of the workers is important to be able to evaluate the risk for health, and do a proper risk assessment. There are several ways to address this issue, for instance:
a) Work place inspection
b) Air sampling
c) Biological sampling
a) Work place inspection
Work place inspections are very useful. During such visits, there are a number of factors to evaluate. While it’s not possible to list everything here, these are some of the main issues to consider:
What types of pesticides are used? How toxic are they?
How many workers are exposed to the pesticides and how and for how long?
Are the workers protected against pesticide exposure during their contact with the substances? Here ventilation systems must be evaluated as well as the access to personal respiratory equipment (gloves, masks, overalls, goggles).
Are the workers exposed to pesticides trained in the risk of this type of work?
Are the workers trained in how to protect their health?
Have workers access to water for cleaning themselves after pesticide exposure? Do they have access to hand washing or shower?
Are the pesticides stored safely? In a locked storage? Where is the key kept?
Some countries have specific regulations related to handling of pesticides, and in such situations, we must evaluate how the requirements in the regulations are followed. It can for instance be regulated by law that the storage room for pesticides should be locked, so no one can enter the room and become exposed to these toxic substances by accident.
Unfortunately intoxications among children has been a problem in places where they play around in such areas.
b) Air sampling
Air sampling of pesticides is possible, when it comes to a few types. In general, air sampling may be difficult. It requires specific laboratories to do the analyses, and in many countries these are not available. Also, it might be quite difficult to know what kind of substances to sample. Many agricultural work places use a number of pesticides, and they may differ as the pests may differ. In a recent study of flower farms in Ethiopia, we found that about 50 pesticides were in storage there, and they constantly changed which one to use. Pesticides are present in the atmosphere at concentrations which are quite low. Because of these low concentrations, pesticides in ambient air are most frequently sampled by specific high volume samplers. Sampling can be done on coal tubes for some types, and radio-assay methods can be used. At present, these surveillance methods are not recommended.
c) Biological sampling
Biological sampling is possible for some pesticides, and is used in several developing countries as a surveillance method. This is the case for the two groups of insecticides; organophosphates and carbamates, as both are acetylcholinesterase inhibitors. It is possible to monitor effects of these pesticides by measurement of acetylcholinesterase activity (IU/mL) in blood or plasma. Specific laboratories analyzing such samples exist in many large cities. Decreases in acetylcholinesterase activity indicate that the worker is exposed to these pesticides. The method requires that one compare the levels to the individual’s own baseline, generally parallel the potential severity of toxicity. Clinical symptoms requiring hospitalization are usually associated with depletions of more than 50% of the normal acetylcholinesterase activity.
Blood samples are important as a surveillance method for some pesticides (Photo: G. Tjalvin)
Workers should be examined with a test before starting this type of work, and testing should be done every 3-4 weeks during intensive exposure periods, preferably within 3 days after application of a pesticide of this type. If this method is used for surveillance, it is important to know when the sample has been taken and when the exposure to these pesticides has taken place – to be able to interpret the results.
There are many methods to prevent intoxications from pesticides. Some short information is given in the following points:
One question can always be asked, related to toxic substances: Are they really needed, or can other, less toxic substances be used? To find less toxic substances is important preventive work. DDT, for instance, was very much used earlier. When we obtained knowledge about all the serious side effects from this pesticide, DDT was banned in most countries, and other pesticides are used instead.
b) Organization of the work
How can the work be performed so as few as possible become exposed to the toxic substances?
This is important; sometimes intoxications occur more frequently among those not directly involved, who stay nearby workers that handle the toxic substances. Accidental exposure to other workers must be avoided. Enclosure of sprayed areas in greenhouses, for instance, is important. It is also important not to enter the greenhouses after spraying until the exposure has been reduced. The “re-entry time” differs from substance to substance and varies with the amount of pesticide sprayed. To have tractors with a hut separating the worker from the exposure in the air is a good way of organizing the spraying work in the field.
Spraying pesticides in a field, using a tractor with a closed cabin. This prevents the driver from pesticide exposure. © Colourbox
c) Education and training
Workers need education in handling toxic substances. Only by education they will fully understand how to protect themselves and the consequences of exposure. Some countries have made education concerning use of pesticides compulsory for persons who purchase and use such substances. Without a certified course, no one can buy pesticides in larger amounts.
d) Protective equipment
Correct protective equipment is of importance. For instance, sprayers of pesticides need overalls and gloves to avoid skin absorption of the substances in the air. They also need respiratory protection during spraying. This equipment must be of the correct type. If filter masks are used, the correct filter must be used, and the filters must be changed often and kept in an airtight box when not in use
Spraying pesticides on fruit trees, using proper protective equipment; overall, gloves and a respiratory mask. This prevents the sprayer from exposure. © Colourbox
e) First aid equipment
Access to water and atropine is of importance, to be able to give first aid if a serious acute intoxication occurs.
f) National plan and policy; regulations
What is most important in this preventive work is that the authorities in each country develop plans for how to reduce pesticide intoxications and implement regulations. Without regulations of this type, the workers will not be fully protected.
© University of Bergen/Author: B.E. Moen