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Costa Rica is a small country in central America, nestling between Panama to the north and Nicaragua to the south and bounded to the east and west by the Pacific and Caribbean oceans. Its coastal plains lead to four mountain ranges running north to south that, combined with the tropical/subtropical climate, have produced a fertile environment for both flora and fauna. Although the country is about the same size as Denmark or West Virginia, it accounts for more than 5% of the world's biodiversity, including 1000 types of orchid, 2000 types of trees and more than 200 species of animals. The government has recognised the importance of their natural inheritance and has set aside about 25% of the country as protected areas and national parks, encouraging ecotourism and boosting the economy. Tourists alone are not sufficient to sustain the country, which also relies heavily on agriculture, with sugarcane, coffee, rice, pineapples and bananas as major crops. However, growing crops in this climate requires the extensive use of pesticides. In fact, the levels of plant protection in Costa Rica are greater than in most industrialised countries, creating a substantial threat to the diverse wildlife. This danger has been recognised by scientists from Canada and Costa Rica itself, who have undertaken a study to sample the distribution of pesticides in air and soil around the country. At first, they looked at the banned organo-chlorine pesticides aldrin, chlordane, dieldrin, nonachlor, HCH, lindane, DDD and DDT and related species and found that levels of these compounds are low and probably related to low historical usage. In the next stage, the research team measured levels of three current-use pesticides and the data from both studies were published in consecutive papers in Environ. Sci. Technol., as described by senior reporter Frank Wania. The 23 sampling sites were selected to represent the wide variation in conditions, including temperature, precipitation, vegetation cover, soil properties, altitude, exposure to prevailing winds and proximity to pesticide usage. Pesticides trapped in passive air samplers and extracted from soil were analysed for the insecticide endosulfan and its breakdown product endosulfan sulphate by GC-ECD. The concentrations of the fungicide chlorothalonil and the herbicide dacthal were measured by GC/MS with negative chemical ionisation in selected ion monitoring mode. In this case, the pesticide concentrations were far higher than expected. For endosulfan in particular, the air levels were much greater than those reported recently in North America. The team were also surprised to find that the highest soil concentrations of all three pesticides were not in the lowlands where the pesticides were applied but at elevations above 2500 m. At two volcanoes which have forested sides (montane forests), Poas and Barva, the concentrations were well above the national average. These high-load sites lie to the west of the extensive banana plantations of the lowlands, in the direction of the prevailing winds, suggesting the existence of atmospheric transport followed by wet deposition, even though the transport is going uphill. This was supported by calculations based on a contaminant fate model which indicated that chemicals with a log(KAW) value between -3 and -5 have a greater propensity for accumulation at altitude (KAW is the air-water partition coefficient). Once there, they are deposited in the rain. There have been several reports that the numbers of amphibians living in montane areas, including Costa Rica, are in decline. In the tropics, the decline tends to be more marked at higher altitudes. Various reasons have been given but now, say Wania and his colleagues, atmospheric transport of pesticides should also be considered as an important factor, especially when the areas of concern are downwind from major areas of pesticide application. Related links:
The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.
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 The Poas volcano in Costa Rica
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