Year: 2011
Type: book-chapter
Abstract: Considerable consistency across studies has been observed for many health endpoints including total mortality, cardiopulmonary mortality and morbidity.Moreover, air pollution studies suggest that the opposite ends of the age spectrum are more susceptible than the general population (Dockery and Pope 1994;Saldiva et al. 1995;Schwartz et al. 1994).Therefore, fetuses are thought to be a vulnerable subgroup of the population who could be most endangered by the effects of air pollution (Pope 2000).Early studies had shown that maternal active and passive smoking could impair reproductive outcomes.Thus, there is a strong belief that prenatal exposure to air contaminants, which is similar to the effects of maternal smoking, can also lead to some adverse pregnancy outcomes.The number of studies linking air pollution with adverse pregnancy outcomes has recently grown steadily since the late 1990s.The adverse effects of air pollutants including particulate matter (PM), nitrogen oxide (NOx), sulfur dioxide (SO 2 ), carbon monoxide (CO), and ozone (O 3 ) on measures of fetal size, gestational duration and other reproductive outcomes have been studied.Adverse reproductive outcomes including low birth weight (LBW: birth weight <2,500g) or preterm delivery (PTD: birth at <37 weeks of gestation) have arisen fairly consistently in recent years.During 1990During -2006, the rates have risen 21% for PTD and 19% for LBW in the United States, respectively (Martin et al. 2008).Studies have suggested that LBW or PTD has been associated with not only childhood mortality and morbidity but also the risk of diseases in adulthood such as heart diseases and diabetes (Clapp Iii and Lopez 2007;Osmond and Barker 2000;Rinaudo and Lamb 2008;Thompson 2007).The prevention of adverse pregnancy outcomes is a renewed national and international priority in maternal and child health (Damus 2008).There is an emerging need to identify the etiological factors of adverse birth outcomes such as environmental exposures, which could be modifiable in order to help reverse the increasing rates. www.intechopen.comThe Impact of Air Pollution on Health, Economy, Environment and Agricultural Sources 94In this chapter, we review the health effects of ambient air pollution on pregnancy outcomes such as LBW, very low birth weight (VLBW: <1,500g), small for gestational age or intrauterine growth retardation (SGA or IUGR, i.e. birth weight below the 10 th percentile for that gestational age), PTD, and birth defects.Further, we discuss the potential biological mechanisms underlying the associations between air pollution and adverse reproductive outcomes.Finally, we briefly introduce the methodology including study designs, exposure measurements, windows of exposure, confounders, and future directions for study of air pollution and pregnancy outcomes. Health effects of air pollution on birth outcomesBirth outcomes, including outcomes of fetal size such as LBW, VLBW, SGA, and IUGR, outcomes of gestational age such as PTD, and birth defects, have frequently been studied in epidemiological research on health effects of air pollution.The associations between air pollution and these birth outcomes may suggest different etiologic and pathogenic mechanisms.Moreover, air pollution is a mixture of pollutants, which also vary in nature and possible health effects.Therefore, existing evidence of health effects of air pollution on birth outcomes are briefly examined by types of birth outcome and/or criteria air pollutants including PM, NO x , SO 2 , and CO as below.Although the associations between O 3 exposure and birth outcomes have also been investigated by several studies, available evidence seems only to support an association with birth defects (Shah and Balkhair 2011).Therefore, the health effects of O3 are merely discussed for birth defects. Health effects on fetal size -LBW, VLBW, SGA and IUGRThe effects of ambient air pollutants on fetal size, specifically LBW have been well studied during the past decades.Overall, there were some positive findings, which suggest that air pollution exposure, through all periods during pregnancy, is associated with adverse health effects on fetal size including LBW, VLBW, SGA and IUGR.However, air pollution consists of many components, making it difficult to pinpoint which pollutant can actually affect fetal size.Therefore, we present below the results from some selected studies by criteria air pollutants individually. Particulate matter (PM)PM generally attracts much more attention in epidemiological research of air pollution because of its physical and chemical characteristics of consisting of organic and inorganic components.The effects of PM on birth outcomes have been reported to be more pronounced compared to other pollutants.Several exposure indices of PM such as total suspend particles (TSP), particulate matter smaller than 10μm aerodynamic diameter (PM 10 ) and smaller than 2.5μm aerodynamic diameter (PM 2.5 ) have been used in studies.Wang et al firstly reported that exposure to TSP in the third trimester of pregnancy was significantly associated with LBW (Wang et al. 1997).After that, many studies have been conducted to report associations between particulate air pollution and LBW, SGA, as well as IUGR.Bobak et al found that annual concentration of TSP during the year of birth was associated with an increased risk of LBW (Bobak and Leon 1999).Rogers et al also found that annual TSP in the year of birth is associated with the risk of LBW (Rogers et al. 2000).Consistent evidence on adverse health effects of PM on birth weight has been reported when PM 10 and PM 2.5 have been used as measures of exposure.Mannes et al found that each 1 μg/m 3 www.intechopen.com
Source: InTech eBooks
DOI: 10.5772/17803
Authors: Xiaohui Xu, Haidong Kan, Sandie H
Institutions: University of Florida, Fudan University
Language: English
Subfield: Health, Toxicology and Mutagenesis
Field: Environmental Science
Domain: Physical Sciences
Open Access status: hybrid
Funder: University of Florida
OpenAlex ID: W1512576304