How are Environmental Factors Linked to Asthma? (Lucas Neas - ORD)
Genetic factors, viral and parasitic infections, diet, lifestyle, air pollution, and allergen sensitization are all linked in some way to asthma. However, none of them alone can be considered the source of the recent upward trend in asthma cases. While genetics are certainly a factor, they do not change quickly enough for a genetic shift to be the cause of the trend. However, genetic factors predispose people to asthma, who are then forced over to active asthma by an increasingly “adverse” environment.
The decrease in infections, due to vaccination and smaller families, means that there has been an overall decrease in the necessity for an immune response to certain diseases. This may sensitize the body to asthma-related allergens. However, this decrease has occurred since the 1960s while the asthma trend is more recent. With regard to diet, it has been found that antioxidants are more protective and an increase in trans-fatty acids, salt, and sugar in the diet due to junk food may be a risk factor. There has certainly been an increase in the consumption of junk food in the United States since the 1960s, but there is a question as to whether this would explain the worldwide trends. The levels of exposures due to indoor and outdoor antigens may have increased, including on an occupational and even community-wide level. Early childhood exposures to dust mites, humidified homes, cockroaches, cat dander, mold spores, and pollen may have increased. However, this does not explain why asthma incidence seems to increase after moving from an urban poor environment to a rich environment. This phenomenon has been seen in Ghana. Other research has looked at lifestyle causes, such as the lack of general time outdoors, particularly spent engaging in vigorous activity. Data have shown that living on a farm provides protection from asthma; this may mean that today’s children spend too much time on indoor activities which increases their exposure to indoor pollutants over time. In addition, pulmonary “exercise” results from general time outdoors. However, if outdoor activity is promoted, it is necessary to ensure that the ambient environment is not polluted.
The decrease in infections, due to vaccination and smaller families, means that there has been an overall decrease in the necessity for an immune response to certain diseases. This may sensitize the body to asthma-related allergens. However, this decrease has occurred since the 1960s while the asthma trend is more recent. With regard to diet, it has been found that antioxidants are more protective and an increase in trans-fatty acids, salt, and sugar in the diet due to junk food may be a risk factor. There has certainly been an increase in the consumption of junk food in the United States since the 1960s, but there is a question as to whether this would explain the worldwide trends. The levels of exposures due to indoor and outdoor antigens may have increased, including on an occupational and even community-wide level. Early childhood exposures to dust mites, humidified homes, cockroaches, cat dander, mold spores, and pollen may have increased. However, this does not explain why asthma incidence seems to increase after moving from an urban poor environment to a rich environment. This phenomenon has been seen in Ghana. Other research has looked at lifestyle causes, such as the lack of general time outdoors, particularly spent engaging in vigorous activity. Data have shown that living on a farm provides protection from asthma; this may mean that today’s children spend too much time on indoor activities which increases their exposure to indoor pollutants over time. In addition, pulmonary “exercise” results from general time outdoors. However, if outdoor activity is promoted, it is necessary to ensure that the ambient environment is not polluted.
Air pollutants have been considered as asthma triggers. However, air pollution has decreased over the past decade while asthma cases and severity have increased. For example, the dramatically cleaner air that resulted from the shutdown of many plants in the former East Germany did not result in changes of asthma rates. In fact, while eastern Germany has more bronchitis and wheeze associated with airborne irritants, they also experience lower rates of asthma and hay fever than in western Germany. In addition, New South Wales, Australia has high rates of asthma but a clean environment.
The Harvard Six-Cities Study and 24-City Study in the United States and Canada looked at the prevalence of respiratory illness in children vs. air pollution. Bronchitis was associated with air pollutants but asthma was not. A study performed in Kanawha County, West Virginia showed an association between volatile organic compounds (VOCs) and other traffic-related pollution and asthma on a city-wide scale.
Based on these studies, it appears that air pollutants may play a greater role as a trigger or exacerbation of asthma but not as a cause, although they may increase the possibility of sensitization to antigens and bioaerosols. Air toxics, such as those associated with traffic, present an area needing further study.
Environmental Factors Linked to Asthma
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