Are there sensitive subgroups for the effects of airborne particles?

Recent studies have shown that particulate air pollution is a risk factor f or hospitalization for heart and lung disease; however, little is known abo ut what subpopulations are most sensitive to this pollutant. We analyzed Me dicare hospital admissions for heart disease, chronic obstructive pulmonary disorders (COPD) and pneumonia in Chicago, Cook County, Illinois, between 1985 and 1994. We examined whether previous admissions or secondary diagnos es for selected conditions predisposed persons to having a greater risk fro m air pollution. We also considered effect modification by age, sex, and ra ce. We found that the air-pollution-associated increase in hospital admissi ons for cardiovascular diseases was almost doubled in subjects with concurr ent respiratory infections. The risk was also increased by a previous admis sion for conduction disorders. For COPD and pneumonia admissions, diagnosis of conduction disorders or dysrhythmias increased the risk of particulate matter < 10 mu m in aerodynamic diameter (PM10)-associated admissions. Pers ons with asthma had twice the risk of a PM10-associated pneumonia admission and persons with heart failure had twice the risk of PM10-induced COPD adm issions. The PM10 effect did not vary by sex, age, and race. These results suggest that patients with acute respiratory infections or defects in the e lectrical control of the heart are a risk group for particulate matter effe cts.