Academic journal article Environmental Health Perspectives

Birth Weight Following Pregnancy during the 2003 Southern California Wildfires

Academic journal article Environmental Health Perspectives

Birth Weight Following Pregnancy during the 2003 Southern California Wildfires

Article excerpt

BACKGROUND: In late October 2003, a series of wildfires exposed urban populations in Southern California to elevated levels of air pollution over several weeks. Previous research suggests that short-term hospital admissions for respiratory outcomes increased specifically as a result of these fires.

OBJECTIVE: We assessed the impact of a wildfire event during pregnancy on birth weight among term infants.

METHODS: Using records for singleton term births delivered to mothers residing in California's South Coast Air Basin (SoCAB) during 2001-2005 (n = 886,034), we compared birth weights from pregnancies that took place entirely before or after the wildfire event (n = 747,590) with those where wildfires occurred during the first (n = 60,270), second (n = 39,435), or third (n = 38,739) trimester. The trimester-specific effects of wildfire exposure were estimated using a fixed-effects regression model with several maternal characteristics included as covariates.

RESULTS: Compared with pregnancies before and after the wildfires, mean birth weight was estimated to be 7.0 g lower [95% confidence interval (CI): -11.8, -2.2] when the wildfire occurred during the third trimester, 9.7 g lower when it occurred during the second trimester (95% CI: -14.5, -4.8), and 3.3 g lower when it occurred during the first trimester (95% CI: -7.2, 0.6).

CONCLUSIONS: Pregnancy during the 2003 Southern California wildfires was associated with slightly reduced average birth weight among infants exposed in utero. The extent and increasing frequency of wildfire events may have implications for infant health and development.

KEY WORDS: air pollution, birth weight, fetal growth retardation, fires, particulate matter, pregnancy outcomes. Environ Health Perspect 120:1340-1345 (2012). http://dx.doi.org/10.1289/ehp.1104515 [Online 29 May 2012]

In late October 2003, a series of wildfires burned > 750,000 acres of forest in Southern California (Blackwell and Tuttle 2003). Strong Santa Ana winds carried the resulting plumes of smoke toward Los Angeles and Orange counties, where a large urban population was exposed to elevated concentrations of air pollutants from the fires (Phuleria et al. 2005). An in-depth exposure assessment study estimated the population-weighted particulate matter (P[M.sub.10]; PM with aerodynamic diameter [less than or equal to] 10 [micro]m) and fine particulate matter (P[M.sub.2.5]; PM with aerodynamic diameter [less than or equal to] 2.5 [micro]m) concentrations, respectively, at 190 and 90 [micro]g/[m.sup.3] under heavy smoke conditions, and 125 and 75 [micro]g/[m.sup.3] under light smoke conditions, compared with baseline concentrations of 40 and 20 [micro]g/[m.sup.3] in the same region (Wu et al. 2006). Using that exposure assessment, a study (Delfino et al. 2009) of cardiorespiratory health effects estimated that elevated P[M.sub.2.5] levels led to a 34% increase in hospital admissions for respiratory conditions 1-2 days later, with the largest associations observed among the very young (0-4 years, 8.3% per 10-[micro]g/[m.sup.3] increase in P[M.sub.2.5]) and very old (65-99 years, 10.1% per 10-[micro]g/[m.sup.3] increase in P[M.sub.2.5]); limited evidence supported a small increase in admissions for cardiovascular conditions as well (Delfino et al. 2009). A separate study found that parental recall of the smell of smoke during these fires was associated with increased medication usage, eye and respiratory symptoms, and physician visits among their children (Kunzli et al. 2006).

Health effects of wildfires. Particulate matter (PM) is possibly the most important health-related component of wildfire events (Naeher et al. 2007). Wildfire-generated PM may be more toxic, on an equal-mass basis, than ambient PM collected in the same region during non-fire periods (Wegesser et al. 2009), potentially due to the role of atmospheric photochemistry resulting in the formation of secondary pollutants (Wegesser et al. …

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