MDH examined years of Minnesota state cancer registry data f
MDH examined 20 years of Minnesota state cancer registry data, from 1988 to 2008, in the two zip codes that encompass the NMCVI study area, using the Minneapolis-St. Paul metropolitan area age-spe-cific cancer rates for comparison. We observed a significant excess of lung cancers among men (398 observed, 325 expected), but not in women, and a significant excess of mesotheliomas among women (8 observed, 3 expected), but not in men (Minnesota Department of
Environmental Research 175 (2019) 449–456
Health, 2011). The unexpected excess of mesothelioma observed in women supports the hypothesis that cumulative, lower level exposure to LAA may increase risk as has been suggested by similar observations in Libby and at other processing sites in the U.S. (Naik et al., 2017; Peipins et al., 2003; Ryan et al., 2017; Szeinuk et al., 2017; Vinikoor et al., 2010). In the present study, we extend our investigation of health impacts in the NMCVI cohort using record linkage with the Minnesota Cancer Surveillance System and with death records to measure the sex-specific occurrence of asbestos-related cancer incidence and mortality. Using environmental and occupational exposure history and assessment data, we examine whether excesses observed may be associated with low level cumulative exposures to LAA and whether a history of occupa-tional asbestos exposure may play a role.
From 2001 to 2004, MDH interviewed Pepstatin-A members who lived in close proximity to the WM/WRG facility at any time from 1938 to 2001, lived on a contaminated property, or had a history of direct handling or contact with the waste rock. The study area encompassed 1983 occupied residential properties located within approximately one-half mile of the facility. In an ancillary investigation, MDH enrolled and interviewed workers and persons living in the same household. In total, there were 6714 eligible participants identified and enrolled in the NMCVI cohort through door-to-door visits with residents, telephone contacts with former residents and workers, community meetings, media reports, WM/WRG company records and public records. Trained interviewers used a questionnaire to collect detailed residential and occupational histories, smoking status, and exposure histories. Possible occupational exposure was determined based on yes/no questions asking whether the participant had ever worked in professions com-monly known for asbestos exposure. Proxy interviews with next of kin were conducted for deceased individuals who met eligibility criteria and, in addition to the exposure history, the decedents' social security number and date and cause of death were collected for later use in data linkage. MDH's previously published descriptive analysis reported vital status, years/months of residence in the study area and proximity to the facility, frequency of direct contact with waste, age at first exposure for playing on waste rock piles, and exposure through multiple pathways of the entire cohort (Kelly et al., 2006; Minnesota Department of Health, 2005). r> This current study was limited to 5848 members of the NMCVI cohort who were alive on January 1, 1988 and they, or their next of kin, consented to record linkage to assess health and mortality outcomes. The Minnesota Department of Health Institutional Review Board ap-proved the study.
2.2. Cumulative asbestos exposure levels
Cumulative ambient asbestos exposure levels (measured in f/cc x months) were calculated for 5161 of 5848 individuals in the study cohort, based on total months of residency (duration) and addresses in the study area, and using results of modeled ambient asbestos con-centration levels during three different time periods during plant op-erations (1938–1989), as described elsewhere (Adgate et al., 2011). The models incorporated prevailing wind patterns and plant emissions during all production years (1938–1989), with peak emissions occur-ring between 1938 and 1972, prior to the installation of air pollution-control equipment.
There were 687 individuals excluded from this exposure analysis whose cumulative ambient fiber exposure could not be estimated due to an in-complete residential history or they reported no history of living in the study area (exposure from direct handling of vermiculite processing waste
or occupational exposure only). We calculated arithmetic and geometric means of ambient exposure in fibers/cc x month to describe ambient ex-posure differences by birth year, gender, and by activity exposure cate-gories to examine how cumulative ambient exposure varies with other exposure pathways (Table 1). Activity exposure categories included a re-ported history of work at WM/WRG, household contact with a WM/WRG worker, direct contact by moving or using waste rock, installing vermiculite insulation, or playing on waste piles in childhood.