risk assessment of malathion

Risk Assessment of Malathion

            Genericville city has a cosmopolitan population of about 100, 000 people and is highly dependent on tourism.  The city has a large river following through the central hub.  In certain places along the river banks of the city, there are marshlands or wetlands that help the excess water from the river to accumulate during period of flooding.  These wetlands, a delicate ecosystem, help to provide home and nutrition for various plants, animals, birds, and fish.  The marshes provide good breeding grounds for fish and birds.  Besides it is also popular with the eco-tourists who want to experience the beauty of the area without destruction of the environment.  However, the marches in Genericville city also act as a breeding ground for mosquitoes which can be a haven for various infections such as West Nile fever.  As per the CDC in 2006, more than 4200 were affected with the disease and about 177 died.  Birds also play a vital role in the transmission of the infection.  The Genericville community including poor and the rich are at a risk of getting infected with the virus (Appendix B).

            It was proposed to launch a program in Genericville to help eradicate West Nile Fever from the area.  The estimated benefit from such a program would mean that the number of mosquitoes in the area would reduce by about 90%, with a reduction of cases of West Nile Fever from 50 to 5.  The chances of mortalities from the infection would reduce to below 20%.  The main idea of the program was to reduce the mosquito population by using the organophosphate insecticide Malathion.  However, the risks of getting exposed to Malathion is also high, and further Malathion may possess certain amount of risk of damaging the environment with degradation of human, animal, plant, aquatic and bird health.  However, the Agency for Toxic Substances and Disease Registry, 2005, feels that Malathion can be rapidly degraded to harmless substances in the environment, and controlled use of the same possess very trivial risks to the environment and human health.  Further, the exposure to Malathion can be minimized through educational and awareness programs (Appendix B).

            Today every process or action in life has a risk.  If an event is certain to occur, the risk is said to be 1, and if it is certain not to occur, the risk is said to be O.  Hence, the risk of certain events occurring in the environment is said to lie between 0 and 1.  There are four processes in risk assessment including Hazard Identification, Dose-response assessment, Exposure Assesment and Risk Characterization (Chapter 4.1).

Hazard identification – It is important to determine if exposure to Malathion can increase the risk of adverse health effects (Chapter 4.1).  Malathion has use both in urban and in rural settings.  In rural settings, the insecticide is used to control pests that would damage crops.  The effect of Malathion on the environment is reduced by using minimum levels of the chemical, ensuring that it can be used only on the host crop, and better application techniques.  In urban settings, the insecticide is used to control mosquitoes that can act as vectors for West Nile Fever.  Many homes, recreational centers and urban gardens are using the same since many years.  In the year 2006, the EPA begun to classify Malathion as a suggestive evidence for carcinogenicity, but sufficient evidence for the same does not exist from long-term studies.  Hence, Malathion use for the general public had to be registered, although it did not have a significant risk on human health (APHIS, 2007).

Dose-response assessment – It is important to study if the amount of Malathion exposure would cause an adverse health problem (Chapter 4.1).  In study animals (such as rats and mice), Malathion can cause cancer only when used at very high doses.  Besides, the studies demonstrated that cancer can occur by chance and may not as a result of exposure to Malathion.  Malathion is not a known mutagen that can result in cancer.  As use of Malathion as an insecticide is in very low doses, there is no significant risk that it can cause cancer.  Besides, when used in the environment, Malathion can degrade rapidly and hence does not pose a risk to even bird health.  There may be a risk to certain beneficial organisms and aquatic life.  Malathion under certain conditions (if not used in a pure form or when disposed off into chlorinated water) may breakdown into malaoxon which is several times toxic than Malathion.  The way in which Malathion is used and the low-level of the substance in various insecticide products would mean the risk from malaoxon is also negligible.  Studies have demonstrated that the risk to any non-target organism in the environment would also be low (APHIS, 2007).

Exposure assessment – it is important to determine how much and how often humans are exposed to the Malathion in the environment (Chapter 4.1).  Malathion would be directly used in area having mosquito breeding grounds, which includes wetlands away from human populations.  The insecticide would be used in very trivial quantities such that the target organisms (Mosquitoes and other vectors) are attacked and non-target organisms (such as birds and aquatic life) are not affected.  As Malathion would not be directly used on the non-target organisms and the fact that Malathion is used in very low concentrations, in least-damaging techniques and ability to undergo breakdown quickly in the environment, the insecticide would be effective on lowering the numbers of mosquitoes breeding in the marshlands, but at the same time have a negligible damaging effect on the environment.  Malathion can be applied by spraying trucks or aircraft-mounted sprayers.  Human exposure and exposure to animals and aquatic life in the environment would be trivial (APHIS, 2007).

Risk characterization – It is important to determine the chances of having adverse health effects based on the dose-response assessment and exposure assessment (Chapter 4.1).  As the drug would be utilized in very low concentrations and that to not directly on human populations (or bird or aquatic populations), the risk of adverse effects would be minimized (APHIS, 2007).

            Based on the information that the City of Genericville is facing an epidemic of West Nile Virus Fever, and that an effective solution in the form of Malathion is available to control the mosquito population without significant risk to the environment (including human, plant, bird, animal and aquatic life), I support a vote for using Malathion in pest control programs.    Currently, there no significant risk, as Malathion is not noted to cause cancer, except in vey high-doses in study animals.  The intention of having this program along with several other issues being handled including:-

·         Educating the population about West Nile Virus Fever

·      Pest control in homes by other means (Use of mosquito nets, keeping doors/windows closed at dusk or dawn hours, removing stagnant water, etc)

·      Providing primary healthcare services including diagnostic, treatment and preventive interventions for West Nile Fever

·      Ensuring research and development – seeking a vaccine against the West Nile Virus, better and less harmful insecticides, etc

·         Monitoring bird, plant, and aquatic health

·         Environment protection of the marshlands

·      Educating the tourists about ways of protecting themselves from West Nile Fever and also about environmental protection


Animal and Plant Inspection Service (2007). EPA’s Risk Assessment on Malathion, Retrieved on May 7, 2010, from Web site: http://www.aphis.usda.gov/publications/plant_health/content/printable_version/faq_epa_risk_malathion.pdf

Appendix B (provided by you)

Chapter 4.1 (provided by you)


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