2.2.1. Ecological studies

Ecological studies in the USA reported increased mortality from bladder cancer among people living in urban areas compared with rural areas. Blot & Fraumeni (1978) reported increased age-adjusted mortality during 1950–1969 in people living in urban areas compared with rural areas within 3056 counties of the contiguous USA after controlling for several variables in the multivariate regression models, such as ethnicity, occupation, income, and education level. Considering population density as a proxy estimate of urban air pollution (traffic and industrial pollution), Colli et al. (2012) reported significant increases in bladder cancer mortality rates with increases in population density (in quartiles) in 2248 counties of the USA during the period 1950–1994. [The Working Group noted that the interpretation of these findings is limited by the ecological design, the aggregate level of information on exposure to air pollution, and a limited ability to assess the importance of potential confounders, such as smoking. However, there was evidence of increasing risk with increasing population density in the study of Colli et al. (2012).]

2.2.2. Exposure to traffic

See Fig. 2.1.

Fig. 2.1

Exposure to outdoor air pollution from traffic indicators and the risk of bladder cancer, stratified by adjustment for smoking

Several studies have examined the association between exposure to outdoor air pollution from traffic, using various metrics, and the risk of bladder cancer. Most studies adjusted for smoking (Soll-Johanning et al., 2003; Guo et al., 2004; Castaño-Vinyals et al., 2008; Wilson et al., 2008; Raaschou-Nielsen et al., 2011b), although two studies did not adjust for smoking (Visser et al., 2004; Liu et al., 2009). All but three studies observed an increased risk of bladder cancer (25–40% increase) associated with various metrics of traffic exposure.

2.2.3. Taxi drivers

See Fig. 2.2.

Fig. 2.2

Risk of bladder cancer in taxi drivers, stratified by adjustment for smoking

The studies that evaluated the association between occupation as a taxi driver and the risk of bladder cancer are presented in Fig. 2.2. Both the studies that adjusted for smoking (Schoenberg et al., 1984; Jensen et al., 1987; Silverman et al., 1989a, b; Colt et al., 2004, 2011; Gaertner et al., 2004; Guo et al., 2004; Band et al., 2005; Dryson et al., 2008; Samanic et al., 2008) and those that did not adjust for smoking (Decouflé et al., 1977; Rafnsson & Gunnarsdóttir, 1991; Dolin & Cook-Mozaffari, 1992; Borgia et al., 1994) generally showed an increased risk of bladder cancer.

2.2.4. Bus drivers

See Fig. 2.3.

Fig. 2.3

Risk of bladder cancer in bus drivers, stratified by adjustment for smoking

The studies that evaluated the association between occupation as a bus driver and the risk of bladder cancer are presented in Fig. 2.3. The results of studies that did not adjust for smoking (Decouflé et al., 1977; Wynder et al., 1985; Paradis et al., 1989; Dolin & Cook-Mozaffari, 1992; Soll-Johanning et al., 1998) as well as those that adjusted for smoking (Schoenberg et al., 1984; Jensen et al., 1987; Silverman et al., 1989a; Hrubec et al., 1992; Colt et al., 2004; Gaertner et al., 2004; Guo et al., 2004; Dryson et al., 2008; Samanic et al., 2008; Petersen et al., 2010) were inconsistent.

2.2.5. Truck drivers

See Fig. 2.4.

Fig. 2.4

Risk of bladder cancer in truck drivers, stratified by adjustment for smoking

The studies that evaluated the association between occupation as a truck driver and the risk of bladder cancer are presented in Fig. 2.4. Both the studies that did not adjust for smoking (Decouflé et al., 1977; Vineis & Magnani, 1985; Wynder et al., 1985; Steenland et al., 1987; Rafnsson & Gunnarsdóttir, 1991; Dolin & Cook-Mozaffari, 1992) and those that adjusted for smoking (Schoenberg et al., 1984; Hoar & Hoover, 1985; Coggon et al., 1986; Brownson et al., 1987; Jensen et al., 1987; Schifflers et al., 1987; Claude et al., 1988; Bonassi et al., 1989; Silverman et al., 1989a; Iyer et al., 1990; Hrubec et al., 1992; Kunze et al., 1992; Siemiatycki et al., 1994; Porru et al., 1996; Colt et al., 2004, 2011; Gaertner et al., 2004; Guo et al., 2004; Band et al., 2005; Dryson et al., 2008; Samanic et al., 2008; Cassidy et al., 2009) generally demonstrated an increased risk of bladder cancer.

2.2.6. Other jobs with high exposure to outdoor air pollution

See Fig. 2.5.

Fig. 2.5

Risk of bladder cancer in other jobs with higher exposure to outdoor air pollution, stratified by adjustment for smoking

There were several studies that evaluated the association between other jobs with a priori higher exposure to outdoor air pollution than the general population and the risk of bladder cancer (see Fig. 2.5). Many other jobs were included in this category, including mail carrier, driver, urban police officer, and service station attendant. Both the studies that did not adjust for smoking (Balarajan & McDowall, 1988; Gubéran et al., 1992; Forastiere et al., 1994; Lagorio et al., 1994; Soll-Johanning & Bach, 2004; Pukkala et al., 2009) and those that adjusted for smoking (Jensen et al., 1987; Risch et al., 1988; Burns & Swanson, 1991; Cordier et al., 1993; Porru et al., 1996; Pesch et al., 2000; Kogevinas et al., 2003; Colt et al., 2004; Gaertner et al., 2004; Kellen et al., 2007; Reulen et al., 2007; Wilson et al., 2008) generally demonstrated an increased risk of bladder cancer.