To the list of air pollution's health effects, add another one: loss of sense of smell.

Mexico City residents can't detect subtle smells as well as residents of neighboring Tlaxcala, researchers at Mexico's National University (UNAM) have reported, though the regions are quite similar in both culture and climate. The primary difference: Mexico City has much higher levels of air pollution.

As the Olympic Games approach, China has come under fire for its environmental track record. Tales of Beijing and other cities' infamous pollution and images of highly polluted lakes and rivers have met with demands for action, both within China and internationally, and have produced some meaningful results. Yet another environmental crisis looms: biological invasions. Indeed, while perhaps not as overt as choking smog or pea-green water, the ecosystems of this vast nation are increasingly threatened by invasive species.

The global campaign to eradicate malaria in the 1950s and '60s successfully vanquished the disease from the United States and Europe and substantially reduced it in others – in India and Sri Lanka, for instance, malaria cases decreased by 99 percent. Malaria transmission was nearly wiped out in the subtropics, and it was significantly reined in in parts of the Soviet Union, Latin America, and Asia.

About the insecticide that served as a cornerstone of the campaign, the National Academy of Sciences wrote in 1970: "To only a few chemicals does man owe as great a debt." But the same insecticide has become one of today's most infamous chemicals. It is DDT.

As world food prices reach record highs, concerns over agricultural productivity are mounting. Productivity growth has stagnated as the world’s population has continued to rise, and the wealth generated from economic development is further increasing demand for food. The use of food crops like corn and sugarcane for biofuels production exacerbates the situation. The United Nations estimates that agricultural output will have to rise 50 percent by 2030 to meet this increased demand