{'fraction_non_alphanumeric': 0.019169329073482427, 'fraction_numerical': 0.002129925452609159, 'mean_word_length': 5.347972972972973, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Introduction to Special Issue on Air Pollution Health Risks

Air pollution is among the most important health risk issues for government regulation, both in the United States, where pollution levels have been greatly reduced in the half-century since the Clean Air Act was passed, and in other areas on the world, such as in the fast-growing urban areas of China, India, and other developing countries, where air pollution levels are high and may be increasing.(1) What concentration levels of air pollutants are acceptably protective of human health? High concentrations are clearly dangerous: coal combustion and industrial processes, such as in the London smog episodes of the 19th century, resulted in widespread disease and increased deaths. The health impacts of smoke from combustion may have been an important influence on human evolution. Recently published evidence indicates that modern humans have a genetic alteration not present in other primates (or in Neanderthals or Denisovans) making modern humans less susceptible to the toxic hydrocarbons in smoke.(2) At lower concentration levels the relationship between exposure to air pollutants and health impairment is less certain. Small changes in morbidity and mortality must be compared with pollutant concentrations, and other factors may play a significant role in causing the changes in morbidity and mortality. If the air pollutant levels are reduced, will health be improved? With a causal relationship, the answer should be yes. But if other factors predominate, the answer could be no. Association should be distinguished from causation. While knowledge is emerging on possible mechanisms by which air pollutants might induce morbidity and mortality, the quantitative relationship between the exposure to air pollutants and health impairments leading to earlier death is not yet well understood. Uncertain-