David Mark Environmental Health 4/20/09 Noise and Child Cognition Noise is defined as being “any sound – independent of loudness – that may produce an undesired physiological or psychological effect in an individual and that may interfere with the social ends of an individual or group” (Mitzfelt, 1996). Noise pollution has been increasing over the past several decades throughout the world due to increased sources of noise and urbanization (Goines & Hagler, 2007). In 1971 the World Health Organization reported that “noise must be recognized as a major threat to human well-being” (Suess, 1973). Research clearly demonstrates that loud noise can lead to hearing problems. However, lower levels of noise can also have nonauditory effects. These effects can be physiological, such as hypertension or asthma exacerbation or psychological, such as annoyance (Goines & Hagler, 2007; Ising, Lange-Asschenfeld, Moriske, Born, & Eilts, 2004). This paper will focus on the effects of noise primarily in the school setting from transportation (e.g. cars, planes, trains) and the effect it has on the cognitive performance of children. Such effects include impaired speech intelligibility, decreased reading ability and comprehension, poorer concentration, poorer memory, decreased motivation, and increased annoyance (Stansfled & Matheson, 2003). Background and Extent of the Problem Sound is measured in decibels (dB), which is a logarithmic scale, with 0 being the first audible sound to human ears (Sound, 2006). Because this is a logarithmic scale an increase of about 3 dB is equivalent to a doubling of sound energy, although an increase of 10 dB is perceived as being twice as loud (Suter, 1991). A weighting or filter may be applied to the measurement of sound to account for differences in frequency, as high frequency sounds are more harmful than low frequency sounds. The “A weighting network” is often used as it correlates well with the perception of sound intensity. To measure average loudness over time either equivalent continuous sound level or the day-night average sound level are used. Noise pollution is directly proportional to population density (Suter, 1991). As more of the United States and world population move to urban areas, the problem of noise pollution is increased. A 1990 study estimated that 138 million people in the United States were exposed to a day-night sound level average of more than 55 dB. Data from the 2000 US census showed that 30% of people cited noise as a problem, with 4% stating that noise made them want to change their residence (Goines & Hagler, 2007). One of the most problematic sources of noise is from aircraft. In the United States there has been an increase in the number of people flying per yeat from 250 million in 1975 to 700 million in 2005 (Schmidt, January 2005). The frequency of flights has also increased by 40% since 1990. This problem is not just limited to the United States. A 1995 European study estimated than more than 25% of Europeans were exposed to equivalent noise levels of greater than 65 dBA (Hygge, Evans, & Bullinger, 2002). Traffic noise was highly or moderately annoying to almost three-fourths of the residents Cairo, Egypt (Ma, Tian, Ju, & Ren, 2006). In Tokyo noise

pollution is so problematic that many people wear earplugs during the day (Chepesiuk, January 2005). As society has become noisier over the past several decades, the problem has also become worse in schools in the United States. A 1995 GAO report concluded that the most frequent environmental problem in schools was poor acoustics and noise (Wetherill, 2002). In Europe, there has been increased concern about the effect of noise related to aircraft and road traffic on children, especially in Munich and London (Hygge, Evans, & Bullinger, 2002) (Haines, Stansfeld, Head, & Job, 2002). Unfortunately, much of the information regarding exposure of children to noise is sporadic and not collected systematically (Bistrup & Keiding, 2002). Evidence of a Causal Relationship and Toxicology To examine the toxicology of noise and specifically the cognitive effects that it has on children this paper will review the criteria suggested by Gordis for establishing a causal relationship; temporality, strength of association, dose-response, replication of findings, biologic plausibility, consideration of alternatives, cessation of exposure (Gordis, 2009). This approach will allow for the evidence of the relationship to be reviewed while exploring the toxicology of noise. The first criterion is the temporal relationship of exposure to noise and cognitive outcomes in children. While several cross sectional studies have demonstrated an association between noise level and cognitive outcomes in school children, it has been difficult to examine the temporal relationship. One of the key studies for establishing the temporal relationship was a natural experiment that occurred in Munich, Germany (Hygge, Evans, & Bullinger, 2002). In Munich the old airport was closing and a new one was opening in a different location. Researchers examined the effects of noise exposure prospectively at schools near the old airport site and the new airport site. Reading scores and long-term memory were adversely affected in the schools near the new airport after it opened. To a lesser extent speech perception and short term memory were also impacted negatively. While there is some plausibility that habituation to the noise could occur, measurements taken at 2 years after the new airport opened were worse in magnitude than those take just one year after. This study overall demonstrates a temporal relationship of noise exposure (from the new airport) with worsening cognitive outcomes. The strength of the relationship refers to the magnitude of the effect observed. One study examined children of the same age in the same school, some of whom were in a classroom that faced railroad tracks and was much noisier (Bronzaft & McCarty, 1975). The children in the noisier classroom had an average reading age that was 3-4 months behind the children in the quieter room. A dose-response relationship is typically seen with toxic substances. It is helpful to examine these relationships to understand what levels are safe. Several studies have demonstrated a dose response relationship between noise and cognitive function in children. A cross-sectional study examining the association of noise at home and cognitive performance was conducted with primary school students living around the London Heathrow airport (Matsui, Stansfeld, Haines, & Head, 2004). Children were divided into 3 groups based on the level of noise at home; < 63 dB, 63-66 dB, and > 66 dB. Immediate and delayed recall both showed a

linear trend, with worse performance at higher levels of noise. However no trend or effect was seen with reading comprehension or attention in this study. A dose- response relationship has not been clearly demonstrated by all studies. Another study in London divided schools around the Heathrow airport into 7 different noise contour bands from