title: Air quality, tobacco smoke, urban crowding and day care: modern menaces and their effects on health.
abstract: BACKGROUND
  The known adverse health effects of outdoor air pollution were reduced in the last century by effective legislation and pollution control. Although combustion of biomass fuels in the indoor environment remains a major hazard in developing countries, there has been a change in the nature of the traffic-generated air pollutants in outdoor air in developed countries. The role of day care and siblings in increasing the risk of infection early in life contrasts with protection from allergic disease later.
  
  
  METHODS
  The mechanisms of how these pollutants exert their effects are poorly understood, but there is emerging evidence that the toxic effects may be related to infection. This synopsis discusses the epidemiologic relationship of the menaces of modern living, including air pollution, urban crowding and infection, and will explore some of the mechanisms of how they act synergistically to cause exacerbations of illnesses in individuals with preexisting respiratory conditions, such as asthma. It will also discuss the roles of day care and siblings in relation to respiratory disease risk.
  
  
  RESULTS
  Current evidence suggests that much of the morbidity and mortality related to sources of both indoor and outdoor pollution occur by causing or interacting with respiratory infection and other acute or chronic health conditions, such as asthma.
  
  
  CONCLUSIONS
  Improvements in air quality through efforts to tackle environmental problems such as pollution and tobacco smoke will help achieve better health. Day care and siblings increase infectious disease early in life but are associated with protection against development of allergic disease later.
authors.affiliation: Department of Respiratory Medicine, Queen Alexandra Hospital, Portsmouth, United Kingdom.
authors.forename: Fraser
authors.initials: F
authors.lastname: Brims
authors.forename: Anoop J
authors.initials: AJ
authors.lastname: Chauhan
mesh_terms: D000293:Adolescent; D000328:Adult; D000397:Air Pollution / Q000009:adverse effects*; D001249:Asthma / Q000139:chemically induced; D002648:Child; D002656:Child Day Care Centers; D002675:Child, Preschool; D003441:Crowding; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D012140:Respiratory Tract Diseases / Q000139:chemically induced*; D014028:Tobacco Smoke Pollution / Q000009:adverse effects; D014505:Urban Population
chemical_list: D014028:Tobacco Smoke Pollution