General relationship between health and air quality widely accepted

1. General relationship between health and air quality widely accepted • Empirical estimates should inform public policy • Difficult to establish cause/effect

2. For example: polluted air typically is polluted in a number of ways • Difficult to separate effects of individual pollutants • “External Health Costs of a Steel Mill” studies relationship between operation of steel mill in Utah and local health • Utah Valley is an area in Utah that includes cities of Provo and Orem

3. Steel mill, built in 1940’s, is large source of air pollution in the valley • During winter temperature inversions, mill found to contribute over half total particulate matter in area • PM10, air pollution generally would have greatest health effect on respiratory system • Associated with such diseases asthma, bronchitis and influenza

4. Paper looks at relationship between hospitalizations/deaths and operation of mill • Compares Utah Valley to nearby Cache Valley • Two areas are similar in characteristics that can affect health • Smoking incidence, temperature, housing etc. • Steel mill too far from Cache to affect air quality in area

5. Utah valley violated PM10 standards on average 12 days a year when the mill is open, zero when it is closed • Cache Valley never recorded PM10 violation • The mill closed for a year in 1986

6. Study argues natural experiment might capture effect of mill that are missed by studies based on measured pollution levels • Difficult to measure exactly what’s in the air • PM10 caused by mill may be more toxic than normal • Closing of mill represented large, discontinuous change in air quality

7. Collects hospital admissions data for respiratory and cardiovascular diseases over 1985 to 1991 • Compares statistics when mill is open to when it is closed Summary Statistics