Allen Ryan W, Davies Hugh, Cohen Martin A, Mallach Gary, Kaufman Joel D, Adar Sara D
Faculty of Health Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada.
Environ Res. 2009 Apr;109(3):334-42. doi: 10.1016/j.envres.2008.12.006. Epub 2009 Feb 3.
Traffic-generated air pollution and noise have both been linked to cardiovascular morbidity. Since traffic is a shared source, there is potential for correlated exposures that may lead to confounding in epidemiologic studies. As part of the Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air), 2-week NO and NO(2) concentrations were measured at up to 105 locations, selected primarily to characterize gradients near major roads, in each of 9 US communities. We measured 5-min A-weighted equivalent continuous sound pressure levels (L(eq)) and ultrafine particle (UFP) counts at a subset of these NO/NO(2) monitoring locations in Chicago, IL (N=69 in December 2006; N=36 in April 2007) and Riverside County, CA (N=46 in April 2007). L(eq) and UFP were measured during non-"rush hour" periods (10:00-16:00) to maximize comparability between measurements. We evaluated roadway proximity exposure surrogates in relation to the measured levels, estimated noise-air pollution correlation coefficients, and evaluated the impact of regional-scale pollution gradients, wind direction, and roadway proximity on the correlations. Five-minute L(eq) measurements in December 2006 and April 2007 were highly correlated (r=0.84), and measurements made at different times of day were similar (coefficients of variation: 0.5-13%), indicating that 5-min measurements are representative of long-term L(eq). Binary and continuous roadway proximity metrics characterized L(eq) as well or better than NO or NO(2). We found strong regional-scale gradients in NO and NO(2), particularly in Chicago, but only weak regional-scale gradients in L(eq) and UFP. L(eq) was most consistently correlated with NO, but the correlations were moderate (0.20-0.60). After removing the influence of regional-scale gradients the correlations generally increased (L(eq)-NO: r=0.49-0.62), and correlations downwind of major roads (L(eq)-NO: r=0.53-0.74) were consistently higher than those upwind (0.35-0.65). There was not a consistent effect of roadway proximity on the correlations. In conclusion, roadway proximity variables are not unique exposure surrogates in studies of endpoints hypothesized to be related to both air pollution and noise. Moderate correlations between traffic-generated air pollution and noise suggest the possibility of confounding, which might be minimized by considering regional pollution gradients and/or prevailing wind direction(s) in epidemiologic studies.
交通产生的空气污染和噪音都与心血管疾病发病率有关。由于交通是一个共同的污染源，存在相关暴露的可能性，这可能导致流行病学研究中的混杂因素。作为动脉粥样硬化与空气污染多民族研究（MESA Air）的一部分，在9个美国社区中的每个社区，主要为了描绘主要道路附近的梯度，在多达105个地点测量了2周的一氧化氮（NO）和二氧化氮（NO₂）浓度。我们在伊利诺伊州芝加哥市（2006年12月N = 69；2007年4月N = 36）和加利福尼亚州里弗赛德县（2007年4月N = 46）的这些NO/NO₂监测地点的一个子集中，测量了5分钟的A加权等效连续声压级（L(eq)）和超细颗粒物（UFP）数量。L(eq)和UFP在非“高峰时段”（10:00 - 16:00）进行测量，以最大化测量之间的可比性。我们评估了与测量水平相关的道路接近度暴露替代指标，估计了噪音 - 空气污染相关系数，并评估了区域尺度污染梯度、风向和道路接近度对相关性的影响。2006年12月和2007年4月的5分钟L(eq)测量值高度相关（r = 0.84），并且在一天不同时间进行的测量相似（变异系数：0.5 - 13%），表明5分钟测量值代表长期L(eq)。二元和连续的道路接近度指标对L(eq)的表征与NO或NO₂一样好或更好。我们发现NO和NO₂存在强烈的区域尺度梯度，特别是在芝加哥，但L(eq)和UFP仅存在微弱的区域尺度梯度。L(eq)与NO的相关性最为一致，但相关性为中等（0.20 - 0.60）。去除区域尺度梯度的影响后，相关性通常会增加（L(eq) - NO：r = 0.49 - 0.62），主要道路下风方向的相关性（L(eq) - NO：r = 0.53 - 0.74）始终高于上风方向（0.35 - 0.65）。道路接近度对相关性没有一致的影响。总之，在假设与空气污染和噪音都相关的终点研究中，道路接近度变量不是独特的暴露替代指标。交通产生的空气污染和噪音之间的中等相关性表明存在混杂的可能性，这可以通过在流行病学研究中考虑区域污染梯度和/或盛行风向来最小化。
