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The International Commission on Occupational Health (ICOH) held its 12th International Symposium on Epidemiology in Occupational Health in Harare, Zimbabwe between 16 and 19 September 1997. The meeting offers an international platform to exchange knowledge about occupational epidemiology. One of the symposia at the conference on pesticides was co-organised with the ICOH Scientific Committee on pesticides through its chair, Professor Maroni of Italy.

Acute effects
Delegates reaffirmed the belief that acute poisoning is a serious problem especially in developing countries. They see a growing concern about the risk of pesticides to human health that has led to some action aimed at promoting their safe use and reducing adverse health effects.

Costa Rica example
Researchers in Costa Rica have analysed pesticide related injuries reported in the Guàpiles region to the National Insurance Company in 1993 and 1996 where about 13,000 people work in agriculture(1). More than 11,000 accidents were reported annually for both years, of which 682 (6%) and 452 (4%) were pesticide related. This meant that pesticide related injuries occurred 5.2 and 3.4 times per 100 agricultural workers respectively.
    Injuries most frequently involved herbicides usually resulting in eye or skin lesions (1.6 and 1.0 per 100 agricultural workers for 1993 and 1996). In about 50% of cases, the herbicide was specified, of which paraquat represented the majority. The incidence of health effects from insecticides and nema-ticides was also high with 0.7 and 1.0 cases occurring per 100 workers during the two years. Most of these involved insecticides such as organophosphates (OPs) and carbamates.
    As a comparison with the US state of California, where about 900,000 farm workers are employed, the annual reported pesticide poisonings is 249 per 100,000 agricultural workers (or 0.249 for 100 workers), according to data taken from the California Agricultural Pesticide Poisoning Surveillance (CAPPS)(2). The sub-group of pesticide mixer-loaders has a relatively higher rate of poisoning at 2,050 per 100,000 (or 2.05 for 100 workers).
    The overall decrease in the reports of pesticide related injuries in Costa Rica might be due to changes in pesticides used, and improvement of working conditions. However, the number of workers covered by the National Insurance Company decreased over the period, possibly leading to under-reporting. Incidence rates are still high and profound changes to reduce the pesticide exposure risks are needed, especially for applicators.

Chronic effects
The impact of long-term occupational exposure to pesticides is more difficult to assess. Researchers reported on their efforts to resolve some of these complex health issues.

Genotoxicity
Ethylenebisdithiocarbamate (EBDC) fungicides can an affect the thyroid and the lymphocyte genome (genetic material) in workers heavily exposed, according to research carried out by the US National Institute of Occupational Safety and Health (NIOSH)(3). NIOSH studied cytogenic (cell-producing) outcomes and thyroid hormone levels among 49 workers spraying EBDCs on tomatoes in Mexico, along with 14 lightly exposed landowners and 31 non-exposed controls.

Reproductive effects
The reproductive function of male greenhouse workers may be at risk from exposure to pesticides, when spraying or nursing cultures, according to research done at the University of Aarhus, Denmark(4).
    Data from 122 men working in 30 greenhouses with ornamental flower production showed that long-lasting, as well as short-term exposure to pesticides reduces semen quality. The researchers warrant caution with this conclusion because no direct documentation of exposure level was possible, and no specific pesticides are mentioned.

Immunotoxicity
Researchers in Italy have studied blood samples from 29 farmers for signs of immuno-toxicity in phenoxy herbicides, OP insecticides, and carbamate fungicides(5). Samples were collected at the beginning of the year, in the absence of exposure, and immediately after each exposure.
    The results confirm that phenoxy herbicides, and to a lesser extent OPs can cause immunological changes to those exposed. The researchers recommend that the health implications and the specific carcinogenic contribution of these effects should be clarified.

Conclusion
According to Dr Rene Loewenson of the Zimbabwean Training and Research Support Centre and Chair of the Scientific Committee of the International Symposium on Epidemiology in Occupational Health: "The symposium provided evidence of acute negative health effects of pesticides that are widespread and often under-reported in routine data systems.
    "Chronic health effects are also significantly more common than is currently recognised in routine health data and extend to possible genotxic, reproductive and immunotoxic effects that need further exploration.
    "Some of the acute and chronic effects are masked or confounded by a high level of background ill health in farm workers, particularly in developing countries, due to poor living and social conditions." (DB)

1. VanWendel de Joode, BN and Wesseling, C., Pesticide Related Occupational injuries in Costa Rica-a comparison between 1993 and 1996.
2. Osorio, AM, Agricultural Pesticide Drift Among Farm Workers in California.
3. Steeland, K, Cedillo, l, Tucker, J, Hines, C, Sorensen, K, Deddens, J and Cruz, V, Altered thyroid hormones and cytogenic profiles in backpack sprayers using EBDC fungicides in Mexico.
4. Abella, A, Ernst, E, Bonde, JP, Semen quality among greenhouse workers.
5. Fano, V, Settimi, L, Rapiti, E, Faustini, N, Farchi, S, Forastiere, F, Pacifici, R, Zuccaro, P, Immunological effects of exposure to pesticides.

[This article first appeared in Pesticides News No. 38, December 1997, page 17]