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EXPOSURE ANALYSIS -CHAPTER 8

Tổ chức Y tế Thế giới (WHO) ước tính rằng khoảng 800.000 người chết sớm xảy ra mỗi năm do ô nhiễm không khí ngoài trời hạt đô thị trên khắp thế giới. 1,6 triệu sinh non trường hợp tử vong do ô nhiễm trong nhà từ việc sử dụng nhiên liệu rắn để nấu ăn và sưởi ấm trong việc phát triển quốc gia. Các nghiên cứu tại nhiều thành phố đã chỉ ra rằng cái chết xảy ra vào những ngày ô nhiễm không khí cao, và các chất gây ô nhiễm chịu trách nhiệm thường được xác định là các hạt | 8 Exposure to Particles Lance A. Wallace U.S. Environmental Protection Agency ret. Kirk R. Smith University of California CONTENTS 8.1 Synopsis.181 8.2 Introduction.182 8.3 Particle Characteristics.183 8.4 Particle Exposures.184 8.5 Studies of the Exposure of High-Risk Subpopulations in the Developed World.186 8.6 Exposure to Particles of Outdoor Origin.187 8.6.1 Separating Indoor from Outdoor Particles in the Measurements.187 8.6.2 The Infiltration Factor.188 8.6.3 The Ambient Exposure Factor.191 8.7 Total Particle Exposure.192 8.8 Reduction of Exposure.192 8.9 Summary.194 8.10 Questions for Review.194 8.11 Answers to Questions for Review.195 References.195 8.1 SYNOPSIS The World Health Organization WHO estimates that about 800 000 premature deaths occur each year due to urban outdoor particle air pollution around the world. A further 1.6 million premature deaths are attributed to indoor pollution from solid fuel use for cooking and heating in developing countries. Studies in many cities have shown that more deaths occur on days of high air pollution and the responsible pollutant is most often identified as particles. Fine particles are created by combustion processes and can evade the body s defenses and penetrate the lungs and bloodstream. The precise mechanisms by which particles cause morbidity and mortality are uncertain and the critical toxic components of the particles are also unclear. Exposure studies are helping to reduce this uncertainty by determining the relationship between personal exposure and the concentrations measured at central site monitors particularly for those people at highest risk. Exposure studies have also identified the most important sources of particles smoking heating cooking and traffic. This chapter reports on the basic studies that have provided most of our knowledge about the sources of indoor particles and the extent of human exposure. It provides the basic mathematical relationship between outdoor and indoor concentrations of