The 15-member European Union agreed in October to set strict limits on ground-level ozone pollution, but Dr. Frank de Gruijl, a professor of dermatology from the Netherlands, says such agreements must be scrutinized and policed with the "utmost vigilance."

That doesn't appear to be happening. One of the major existing problems, says de Gruijl, is illegal trade involving large quantities of ozone-depleting substances. And while developed countries are curbing use of these substances, developing countries have no such safeguards. Sources of ozone depletion include the loss of chlorofluorocarbons from air conditioners, fire extinguishers, foaming and cleaning products, and fumigants used to kill nematodes.

In a recent article (CMAJ 2000;163:851-5) de Gruijl advised consumers in developed countries to "remain vigilant and not purchase anything operating or produced with ozone-depleting substances when good alternatives are available."

The spectre of ozone-depletion came to the fore this fall when 120 000 Chileans were warned to stay indoors during prime sunlight hours. De Gruijl says these warnings are "understandable" in the face of a sixfold increase in the chance of sunburn and the possibility of a temporary depression of cellular immune responses, which could make people more vulnerable to infections.