Exposure to air pollution near a steel plant and effects on cardiovascular physiology: A randomized crossover study

摘要

Background: Iron and steel industry is an important source of air pollution emissions. Few studies have investigated cardiovascular effects of air pollutants emitted from steel plants. Objective: We examined the influence of outdoor air pollution in the vicinity of a steel plant on cardiovascular physiology in Sault Ste. Marie, Canada. Methods: Sixty-one healthy, non-smoking subjects (females/males = 33/28, median age 22 years) spent 5 consecutive 8-hour days outdoors in a residential area neighbouring a steel plant, or on a college campus approximately 5 kilometres away from the plant, and then crossed over to the other site with a 9-day washout. Mid day, subjects underwent daily 30-minute moderate intensity exercise. Blood pressure (BP) and pulse rate were determined daily and post exercise at both sites. Flow-mediated vasodilation (FMD) was determined at the site near the plant. Air pollution was monitored at both sites. Mixed-effects regressions were run for statistical associations, adjusting for weather variables. Results: Concentrations of ultrafine particles, sulphur dioxide (SO_2), nitrogen dioxide (NO2) and carbon monoxide (CO) were 50-100% higher at the site near the plant than at the college site, with minor differences in temperature, humidity, and concentrations of particulate matter ≤2.5 μm in size (PM2.5) and ozone (O3). Resting pulse rate [mean (95% confidence interval)] was moderately higher near the steel plant [+1.53 bpm (0.31, 2.78)] than at the college site, male subjects having the highest pulse rate elevation [+2.77 bpm (0.78, 4.76)]. Resting systolic and diastolic BP and pulse pressure, and post-exercise BP and pulse rate were not significantly different between two sites. Interquartile range concentrations of SO_2 (2.9 ppb), NO_2 (5.0 ppb) and CO (0.2 ppm) were associated with increased pulse rate [0.19 bpm (-0.00,0.38), 0.86 bpm (0.03,1.68), and 0.11 bpm (0.00,0.22), respectively], ultrafine particles (10,256 count/cm~3) associated with increased pulse pressure [0.85 mmHg (0.23,1.48)], and NO_2 and CO inversely associated with FMD [-0.14% (-0.31, 0.02), -0.02% (-0.03, -0.00), respectively]. SO_2 during exercise was associated with increased pulse rate [0.26 bpm (0.01,0.51)]. Conclusion: Air quality in residential areas near steel plants may influence cardiovascular physiology.