Academic journal article Environmental Health Perspectives

Occupational Exposure to Benzene and Non-Hodgkin Lymphoma in a Population-Based Cohort: The Shanghai Women's Health Study

Academic journal article Environmental Health Perspectives

Occupational Exposure to Benzene and Non-Hodgkin Lymphoma in a Population-Based Cohort: The Shanghai Women's Health Study

Article excerpt

Introduction

Benzene is a common occupational solvent that has been used in multiple industries, particularly as a chemical intermediate in the production of plastics and in rubber manufacturing, and has been used as a solvent in common consumer products worldwide (Wilbur et al. 2008). Moreover, exposure to benzene is ubiquitous in the general population because it is present in gasoline, automobile emissions, and cigarette smoke (Wilbur et al. 2008). There has been continued concern regarding potential adverse health effects arising from airborne benzene exposures, particularly in light of evidence that benzene is hematotoxic at exposure levels as low as < 1 ppm (Lan et al. 2004; Qu et al. 2002) and is associated with an increased risk of myelodysplastic syndrome at relatively low exposure levels (Schnatter et al. 2012). In China, benzene is regularly used in manufacturing industries, and historically high levels of occupational benzene exposure have been reported, with a number of reports describing cases of benzene poisoning in exposed Chinese workers (Liu et al. 2009).

Exposure to benzene, which is classified by the International Agency for Research on Cancer (IARC) as a Group 1 carcinogen, has been concluded to cause acute myeloid leukemia (AML), based in part on results from several case-control and occupational cohort studies in a variety of human populations (IARC 2012). In addition, a variety of other adverse health effects associated with benzene have been observed in animal and human studies, including developmental, neurological, and hematopoietic toxicities (Wilbur et al. 2008). Benzene is also a suspect lymphomagen based on positive associations with non-Hodgkin lymphoma (NHL) overall or with specific NHL subtypes observed in some occupational cohort and case-control studies, although the strength of the evidence is not as strong as the association with AML (Baan et al. 2009; IARC 2012). In particular, a significant exposure-response association with NHL was previously identified for benzene exposure in a large occupational cohort study of benzene-exposed workers in China (Hayes et al. 1997). Several more recent case-control studies conducted in the United States and in Europe have provided some additional evidence for an association with NHL overall (Dryver et al. 2004; Fabbro-Peray et al. 2001) or with specific subtypes including follicular and diffuse large B-cell lymphoma and chronic lymphocytic leukemia (CLL) (Costantini et al. 2008; Miligi et al. 2006; Wang et al. 2009). Based in part on these epidemiologic studies, an IARC working group recently concluded that there is evidence for a positive association between benzene exposure and NHL risk in humans (IARC 2012).

To our knowledge, no previous studies have evaluated the association between benzene exposure and NHL in the context of a population-based prospective cohort study with diverse occupational histories. Recently, a unique framework for assessing historical benzene exposure was developed and applied in a population-based cohort study of Chinese women living in urban Shanghai (Friesen et al. 2012). This approach combined a job-exposure matrix (JEM) with short-term area air measurements of benzene in factories in Shanghai over the period 1954-2000, and has been demonstrated to increase contrast in exposure levels between different industries and jobs, as well as over time, compared with using the JEM alone (Friesen et al. 2012). Here, we applied this exposure assessment framework to evaluate the association between occupational exposure to benzene and risk of NHL in this population-based cohort consisting of Chinese women living in Shanghai.

Methods

Study population and outcome ascertainment. Details concerning the study population enrolled in the Shanghai Women's Health Study (SWHS) have been described previously (Zheng et al. 2005). Briefly, the study is a prospective cohort of 74,942 women living in urban Shanghai who were enrolled between the ages of 40 and 70 years, with subject enrollment occurring between December 1996 and May 2000. …

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