It’s been 50 years since cleaning up the air in the United States began in earnest. Skies are much clearer now than in the mid-20th century. Leaded gasoline is gone, power plants have been abandoning coal and sulfur dioxide has dropped by 91%. Despite these growing improvements, why have epidemiologists been unable to show the demonstrable public health benefits that their computer models predict?
Here are some possibilities.
Maybe we’re looking at the wrong pollutants.
EPA has been monitoring essentially the same air pollutants for 50 years. Since 1980, lead in gasoline dropped by 99%, carbon monoxide from traffic by 83%, and nitrogen oxides by 63%. Concentrations of ozone and airborne particulate matter have decreased by about 30% . Traffic is an important source of air pollution and, since 1970, miles driven have more than quadrupled while fuel economy nearly doubled. The composition of engine exhaust has changed but we have only sparse data on the relevant trace metals, various carbon compounds, or the nanometer-sized particles that can enter the bloodstream. Ambient air quality monitoring has been focused on regulatory rather than scientific priorities.
Maybe we’re looking in the wrong places.
EPA regulations, by law, are limited to outdoor air quality. But we spend 85% of our time indoors where air quality can be significantly better or worse, depending on building construction, air conditioning and ventilation, and indoor sources. Indoor air quality is impacted by smoking, cooking, household cleaning, air “fresheners”, and is neither monitored nor controlled, established health effects notwithstanding. For example, the underlying cause of asthma is an allergic reaction often linked to indoor air pollution that is thought to exacerbate other respiratory effects as well.
Maybe we’ve been looking at the wrong people.
Not everyone is affected by polluted air. Excess mortality during the major smog episodes such as the notorious 1952 smoky fog in London was largely limited to those with previous cardio-respiratory conditions. No individual death has been linked with long-term exposure to air pollution, which preferentially impacts the frail and susceptible, often the very young and elderly. Most of the key epidemiology studies were based on healthy middle-class, middle-aged white adults. By and large those studies focus on specific outcomes like mortality and hospitalization rather than identifying mechanisms and interactions that could lead to these events.