It is absolutely true, and there are a number of reasons why, all connected with pesticides.
Firstly there is far less restriction over the types of pesticides that can be used in a lot of coffee and cocoa growing countries, as well fewer safeguards for those that are doing the spraying. The upshot being that a lot of cocoa and coffee plantations are heavily sprayed with pesticides such as DDT and Lindane. These organochlorine pesticides that have long been banned in the EU and USA, are sprayed by workers with little or no protective clothing.
Organochlorines are known to cause nerve damage and to disrupt hormones if used unprotected, and can be particularly harmful to children if they are sprayed around domestic areas. By only buying organic coffee and chocolate you are ensuring that the growers and their families are protected from these dangers.
A lot of pesticides, including the organochlorines, are fat soluble chemicals, as the last thing you want after you have just sprayed your crop is for the valuable pesticides to be washed off by the rain. Fat soluble pesticides bio-accumulate through the food chain, so the snake that eats the bird that eats the insect that got sprayed ends up with very high levels in its fatty tissue. They are therefore very damaging to the entire local ecosystem.
The other key issue with the fat soluble pesticides used on coffee and cocoa is that because of the way both of these crops are processed, they are actually concentrated into the product, meaning that your chocolate bar or cappuccino ends with a relatively higher proportion of pesticide residues than the raw material. Traces of Lindane and DDT are routinely found in finished chocolate and coffee products, but are considered acceptable because they are “unavoidable”. There is a very easy way to avoid them – eat organic.