Pesticides are chemicals designed to kill pests such as insects that harm crops or threaten human health by transmitting diseases when they bite.
They have boosted agricultural output but also pose a range of threats to people, particularly farmers and their families in developing nations, and to the wider environment.
Acute symptoms of pesticide poisoning include headaches, nausea, dizziness and breathing problems. Very high exposures can cause unconsciousness or sudden death.
The World Health Organization says pesticide poisoning causes about 20,000 accidental deaths each year.
Chronic effects linked to long-term exposure include impaired memory, speech difficulties and delayed reaction times.
Some pesticides are of special concern as they have been show in animal experiments to be endocrine disruptors or to harm the body’s nervous system.
There is some evidence to link pesticides with respiratory and skin diseases, cancers, birth defects and reproductive disorders, and it is thought that children are at greatest risk as their bodies are still developing.
In addition to threats to farmers and others who handle pesticides directly, there are concerns for people who live in areas where large quantities of pesticides are sprayed, and for consumers who eat food containing high levels of pesticide residues.
Pesticides can also harm the wider environment by killing non-target species or, in the case of certain endocrine disruptors and persistent organic pollutants, by affecting the reproductive health of wild species.
Pesticide producers argue that their products pose little risk if users follow the safety guidelines, such as wearing protective clothing, gloves and masks.
But the reality in many developing nations is that this does not always happen. The World Health Organization says that tens of millions of cases of pesticide poisoning result, with significant knock-on effects for rural livelihoods and economies.
To promote safer use of pesticides worldwide, the UN Food and Agriculture Organization has developed an International Code of Conduct on the Distribution and Use of Pesticides, and additional guidelines for regulatory authorities, industry and other stakeholders.
Many of the most dangerous pesticides are being phased out or banned and replaced with safer alternatives. These controls are generally stricter in industrialized countries, although some pesticides are now also covered by multilateral environmental agreements, such as the Rotterdam Convention and the Stockholm Convention.
Many of the more modern pesticides are protected by patents and are too costly for farmers in developing countries. There are also concerns that even these newer chemicals can pose significant health threats.
In 2008, the US-based Center for Public Integrity published a large-scale journalistic investigation into the safety of modern pyrethrin- and pyrethroid-based pesticides.
It found that these products accounted for more than 26 percent of all fatal, ‘major’, and ‘moderate’ human incidents reported to the US Environmental Protection Agency in 2007.
Alternatives to chemical pesticides include ‘natural pesticides’ such as extracts from the neem tree, which are toxic to insects, and biological control methods which use natural predators (such as parasitic wasps) to control insect pests.
Another alternative is to use crops that have been genetically-modified to produce a toxin that is deadly to insect pests but harmless to birds and mammals.
The most widely used toxin is called Bt after the bacterium (Bacillus thuringiensis) whose gene researchers have inserted into crops such as ‘Bt cotton’.
This approach is itself controversial, especially to activists who oppose any kind of genetic modification of foodstuffs.
Some organisations advocate changes to farming practices that reduce or eliminate the use of pesticides. Options include integrated pest management, which combines reduced pesticide use with biological control and other methods of pest control, and organic farming, which eliminates pesticide use entirely.
Pesticide-related stories can include coverage of suspected poisoning of farmers, investigations of illegal pesticide sales, reports on pesticide residues on fruit and vegetables and news about regulations and how they are implemented.
A good source for journalists is the Pesticide Action Network (PAN), which lobbies for greater control of hazardous pesticides. It has more than 600 member organizations and regional offices for North America, Latin America, Europe, Africa, and Asia and the Pacific.
PAN’s pesticide database has detailed information about the toxicity and regulatory status of specific chemicals, and for diagnosing pesticide poisoning.
In most countries, the official body charged with regulating pesticides will be part of the agriculture ministry.
For industry views, the CropLife International website has a comprehensive set of information that represents the positions of major multinational pesticide producers.
IISD’s Earth Negotiations Bulletin provides coverage of meetings of the pesticide-related multilateral environmental agreements.
CASE STUDY – Cambodia’s pesticide problems
In 2002 the Environmental Justice Foundation produced a detailed report [pdf] on health threat posed by pesticides in Cambodia. It showed that despite there being a national law that banned the most dangerous chemicals, many farmers were being poisoned by illegal products.
This was due to weak enforcement of national laws that allowed banned products to enter Cambodia from other countries. As these pesticides were labelled in foreign languages the Cambodian farmers could not read the safety information.
The farmers used excessive doses, rarely used any form of safety equipment, and often mixed many chemicals together. Children were at high risk as they were actively using pesticides in the fields and the chemical containers were often stored or discarded after use in areas where they played.
Local organizations and international agencies were promoting integrated pest management and organic farming to reduce the threats posed by pesticides.
EJF report – What’s Your Poison? Health threats posed by pesticides in developing countries [PDF]
World Health Organization pesticides pages
UN Food and Agriculture Organization – Pests and pesticide management