A researcher has discovered unexpectedly large amounts of dandruff and other flaking skin, fur, pollen and similar materials in air pollutants known as aerosols. Aerosols, tiny particles in the air, are widely studied because they are an important factor in regulating climate, variously absorbing heat to warm the air and reflecting sunlight to cool it. They are also important in forming rain and snow. But the amount of cellular material — bacteria, plant fragments, spores, fungi and so forth — had been thought to be only a small proportion compared with mineral dusts, clay and sea salt. Now, Ruprecht Jaenicke...