Nutritious, tasty and healthy, honey can also contain pollutants like heavy metals if the beehives are placed too close to highways or factories, studies have found. Fortunately, pollution that ends up in honey is proportionately small, while honeybees have low tolerance for pollution and often die. Moreover, contrary to popular belief, honey that turns into sugar is not necessarily of poor quality. Exceptionally sensitive to pollutants, bees could be used to gauge the degree of pollution in an area. As Kathimerini learned from agriculturalist Eleftherios Alysandrakis, who has carried out a relevant study, «increased amounts of heavy metals affect the natural functions of a bee. Ozone damages the nervous system of bees and causes loss of appetite.» Bees also cannot tolerate insecticides. According to Paschalis Harizanis, assistant professor of beekeeping at the Agricultural University of Athens, «when an area is sprayed, bees die in the field.» Nevertheless, radionuclides (radioactive contaminants), heavy metals and trace elements are pollutants that could all end up in honey in various ways. A US study has found that the lead content in bees that drew nectar from plants next to a highway was 20 times higher than bees that visited plants 850 meters away. But the percentage of pollutants that end up in the honey is much lower than in other beehive products. Pollen has much higher levels of pollutants, since it has longer exposure to a polluted atmosphere. Unfortunately, the more nutritious the honey, the more likely it is to have pollutants. «Honey derived from coniferous trees, such as pine or fir honey, or chestnut tree honey are more nutritious perhaps because these trees have a deeper root system and absorb more nutrients,» explains Alysandrakis. But for the same reason, these trees also absorb more pollutants. Pine honey is also produced from the resin secreted by the pine, which stays exposed to the atmosphere for long periods of time. The most nutritious honey is that produced by bees that have fed off chestnut trees or heather, but the taste is often off-putting, making it less popular. By contrast, thyme honey tops the list for consumers. Only 10 percent of the honey produced, however, can be called thyme honey. Although many think that honey that turns to sugar has been adulterated, this is in fact a perfectly natural process that has to do with its provenance. Orange honey, for example, turns to sugar very quickly, thyme honey does so in nine months, while pine or fir honey takes years. If stored in a place that is dry and dark, and in temperatures below 10 degrees Celsius, honey can last for a very long time.