Acid rain is a widespread term used to describe all forms of acid precipitation (rain, snow, hail, fog, etc.). Atmospheric pollutants, particularly oxides of sulphur and nitrogen, can cause precipitation to become more acidic when converted to sulphuric and nitric acids, hence the term acid rain. Acid deposition, acid rain and acid precipitation all relate to the chemistry of air pollution and moisture in the atmosphere. Scientists generally use the term acid deposition but all three terms relate to the same issue. Acid rain can have serious impacts on trees and forests. Acid rain does not usually kill trees directly. Instead, it is more likely to weaken them by damaging their leaves, limiting the nutrients available to them, or poisoning them with toxic substances slowly released from the soil. The main atmospheric pollutants that affect trees are nitrates and sulphates. Forest decline is often the first sign that trees are in trouble due to air pollution. Scientists believe that acidic water dissolves the nutrients and helpful minerals in the soil and then washes them away before the trees and other plants can use them to grow. At the same time, the acid rain causes the release of toxic substances such as aluminum into the soil. These are very harmful to trees and plants, even if contact is limited. Forests in high mountain regions receive additional acid from the acidic clouds and fog that often surround them. These clouds and fog are often more acidic than rainfall. When leaves are frequently [...]

Every increase in air pollution kills a few more people; find Demosthenes B. Panagiotakos, PhD, and colleagues at the University of Athens, Greece. For every one-unit increase in carbon monoxide, the researchers suggest, there are two or more extra deaths each day. “These health effects occur even at exposure levels below those stipulated in current air-quality standards,” Panagiotakos says in a news release. “It is unclear whether a safe threshold exists.”

Over a five-year period, the researchers collected daily values of various air pollutants in Athens. They also collected data on heart disease and strokes. The main finding: A 10-unit increase in carbon monoxide ups heart and stroke deaths by 46%. Panagiotakos reported the findings at this week’s Scientific Sessions 2003 meeting of the American Heart Association. The results shouldn’t be a big surprise. Similar studies in other cities reach similar conclusions. A Drag on the Heart For a person who smokes, even a short-term increase in air pollution could mean a heart attack. Yves Cottin, MD, PhD, of the University of Dijon in Burgundy, France, and colleagues collected data on heart attacks that came on bad air days. Not everybody who got heart attacks on these days was a smoker. But pollution was more likely to trigger heart attacks in smokers than in nonsmokers. It’s also a warning for people already at risk of heart attacks to stay indoors and avoid strenuous exercise on bad air days, Cottin says. Tiny particles floating in the air — the kind of [...]