Persistent Organic Pollutants & Breast Cancer Risk

Institution: Cancer Prevention Institute of California
Investigator(s): Peggy  Reynolds , Ph.D. - Peggy  Reynolds , Ph.D. -
Award Cycle: 2010 (Cycle 16) Grant #: 16ZB-8501 Award: $1,910,517
Award Type: SRI Program Directed Awards
Research Priorities
Etiology and Prevention>Etiology: the role of environment and lifestyle

This is a collaboration with: 16ZB-8501A -

Initial Award Abstract (2010)

Persistent Organic Pollutants (POPs) are a large, diverse group of synthetic toxic compounds that include organochlorine pesticides and some industrial chemicals. Originally introduced during the post WWII industrial boom, many of the older POPs, including DDT and polychlorinated biphenyls (PCBs) were banned in the 1970s due to concerns about health effects. These compounds don’t easily break down; they accumulate in the food chain, including people’s body fat. Consequently, most Americans today have detectable levels of these chemicals in their bodies. Polybrominated diphenyl ethers (PBDEs) and other brominated flame retardants (BFRs) are a newer class of POPs, initially introduced in the late 1970s as flame retardant additives to consumer and building products. The concentrations of these newer POPs in human tissue are increasing at an alarming rate and Californians have some of the highest levels in the world. While many of the older POPs are known or suspected carcinogens, their role in the development of breast cancer is uncertain; the health effects of the newer POPs are virtually unknown.

The primary objective of this study is to investigate the risk of breast cancer associated with both the older and newer POPs among participants in the California Teachers Study (CTS), a large on-going study of breast cancer among 133,479 female California professional school employees. We will also look for disparities in, and predictors of, body burden levels of these compounds and explore potentially important windows of susceptibility. Capitalizing on the unique resources collected over the 15 years since the CTS’ inception, this study will measure the levels of POPs in blood collected for two studies already underway. To identify disparities in, and predictors of, body burden levels of PBDEs/BFRs, we will utilize the approximately 360 blood specimens to be collected from CTS participants in 2010. A geographic information system (GIS) will be used to link the residential location of CTS members’ homes to the location of waste processing and manufacturing sites that may serve as sources of PBDE/BFR exposures. Survey and census data will be used to explore behavioral and sociodemographic predictors of body burden levels. Study participants are racially and ethnically diverse and from both rural and urban areas, so that analyses may identify disparities in exposure to these compounds.

These preliminary analyses will help us optimize selection of study subjects for the breast cancer risk analysis. This will be conducted among 2,000 CTS participants who have provided a blood specimen, 1,000 who will have been diagnosed with breast cancer and 1,000 women who remained breast cancer-free (controls) between 2007 and 2013. Concentrations of 15 PCBs, 4 organochlorine pesticides, 11 PBDEs, and 10 BFRs will be measured in their blood. Statistical models will be used to compare the levels of these POPs in women with breast cancer to the control women. Survey information will be used to account for differences in other known risk factors. Additional analyses will evaluate whether certain women may be especially susceptible to risks associated with these exposures due to the type of tumor they have, or by virtue of selected behavioral or genetic characteristics. For a subset of the CTS cohort, we will use questionnaire and birth file data to enhance exposure estimates for earlier time periods that may represent windows of increased vulnerability to the effects of these compounds.

This study is designed to overcome many limitations common to prior studies. By using the large number of biospecimens already being collected through the CTS parent grant, and with Dr. Petreas’ expertise in measuring multiple POPs in a single sample, our study offers an outstanding opportunity to investigate multiple compounds and susceptible subpopulations or potentially important windows of susceptibility. Advanced statistical techniques from genomics offer an innovative approach to the complexities of POPs exposures, which tend to be highly correlated and may act either synergistically or antagonistically to influence risk. This study could be the first large-scale epidemiologic study to evaluate the potential link between PBDEs/BFRs and breast cancer, as well as identify disparities in and determinants of exposure — information critical to public health and regulatory actions aimed at curbing such exposures. Finally, it directly addresses the ongoing concerns of breast cancer and environmental advocates about the role of these chemicals in breast cancer.

Publications:
Time Trends in Per- and Polyfluoroalkyl Substances (PFASs) in California Women: Declining Serum Levels, 2011–2015

Declines in serum PBDEs in older California women may have reached a plateau (2011-2015)




Progress Report 1 (2011)

Activities during the first year of this study primarily have been focused on the following start-up tasks: obtaining IRB approvals; coordinating with collaborating study sites to set up protocols for the selection and delivery of biospecimens from the CTS parent study to our laboratory; laboratory set-up and bioassay pre-processing of initial samples; acquisition of data files for record linkages; and the conduct of preliminary record linkages. Pilot record linkages have been very successful and informative towards optimizing our final linkage strategies. The primary obstacle encountered in this first year of the study was the delay in delivery of biospecimens to our lab from the CTS parent grant. Specimen collection began in May 2011 and to date we have received 90 blood samples designated for our first specific aim, and 487 samples (256 cases/231 controls) for our second specific aim. The first batch of these specimens has undergone preprocessing and the bioassays are poised to begin in December 2011. Since completion of our specific aims is contingent upon the body burden measurements in the blood samples, we have no experimental results to report at this time. The next year of this study will be devoted to completing the record linkages, developing protocols for assigning indoor and outdoor measures of exposure, and conducting the laboratory bioassays on the blood samples as they become available.




Progress Report 4 (2014)

Persistent organic pollutants (POPs) are a large and diverse group of pervasive environmental contaminants with highly toxic properties and widespread human exposures. The primary objective of this study is to investigate the risk of breast cancer associated with body burden levels of POPs (including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs)) among participants in the California Teachers Study (CTS). Ancillary to this main objective is the identification of disparities in, and predictors of, body burden levels of these compounds and the exploration of potentially important windows of susceptibility.

Our specific aims are to: (1.) Describe disparities in, and predictors of, blood levels of PBDEs in a subset of 360 CTS members with no history of breast cancer; (2.) Estimate the risk of breast cancer associated with body burden levels of POPs among the full CTS cohort; (3.) Use questionnaire data and record linkage to birth files for a subset of the CTS to enhance exposure estimates for two potential windows of susceptability including the perinatal and early reproductive years. While our study originally was designed to focus on the OCPs, PCBs and PBDEs, we have also added the perfluorinated compounds (PFCs) to our project.

During the fourth year of this study, we have made steady progress towards all of our specific aims. Addressing our first aim, we examined outdoor correlates of PBDEs through an analysis of PBDE serum levels and residential proximity to solid waste facilities/landfills and toxic release facilities. Using data from the Solid Waste Information System (SWIS) of California’s Department of Resources Recycling and Recovery and the U.S. EPA’s Toxics Release Inventory (TRI) program, we used a GIS to calculate residential proximity (distance in km) of 477 study participants’ residential addresses to the nearest facility and evaluated whether serum levels varied by proximity. Our results suggested that living within 10 km of solid waste facilities/landfills may be related to higher serum levels of two specific congeners of PBDEs (BDE-47 and BDE-100). During this past year, we also have coordinated the shipment of 898 blood samples collected from the parent CTS study to our environmental chemistry lab. Due to the lower than expected incidence of breast cancer in the CTS cohort, case accrual for our study has lagged behind our study’s original timeline. Consequently, we have modified our study protocol to include 500 stored blood samples previously collected from CTS members to augment the on-going biospecimen collection from prospectively-identified cases. During the current reporting period, we have conducted 2,282 bioassays among study participants who are potentially eligible for our risk analyses (aim#2), including 1,207 for PBDEs, 75 for PCBs/OCPs, and 1,000 for PFCs. To address our third specific aim, we have completed linkages to California birth records and have abstracted residential addresses upon which we are currently working to construct a residential history that will be used to inform potential environmental exposures during early reproductive life. We also have completed linkages to California Department of Education Employment records to build a similar history for workplace locations.

Work in the upcoming year of this project will focus on finalizing and disseminating the results from our Aim #1 analyses, obtaining the stored blood samples from the CTS, conducting the bioassays on these and the remaining prospectively-collected blood samples, completing the construction of workplace and residential histories for study participants, and initiating the construction of our analytic datasets upon which the statistical analyses for our second and third study aims will be conducted.




Progress Report 5 (2015)

Persistent organic pollutants (POPs) are a large and diverse group of pervasive environmental contaminants with highly toxic properties and widespread human exposures. The primary objective of this study is to investigate the risk of breast cancer associated with body burden levels of POPs (including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs)) among participants in the California Teachers Study (CTS). Ancillary to this main objective is the identification of disparities in, and predictors of, body burden levels of these compounds and the exploration of potentially important windows of susceptibility.

Our specific aims are to: (1.) Describe disparities in, and predictors of, blood levels of PBDEs in a subset of 360 CTS members with no history of breast cancer; (2.) Estimate the risk of breast cancer associated with body burden levels of POPs among the full CTS cohort; (3.) Use questionnaire data and record linkage to birth files for a subset of the CTS to enhance exposure estimates for two potential windows of susceptability including the perinatal and early reproductive years. While our study originally was designed to focus on the OCPs, PCBs and PBDEs, we have also added the perfluorinated compounds (PFCs) to our project.

During the fourth year of this study, we have made steady progress towards all of our specific aims. Addressing our first aim, we examined outdoor correlates of PBDEs through an analysis of PBDE serum levels and residential proximity to solid waste facilities/landfills and toxic release facilities. Using data from the Solid Waste Information System (SWIS) of California’s Department of Resources Recycling and Recovery and the U.S. EPA’s Toxics Release Inventory (TRI) program, we used a GIS to calculate residential proximity (distance in km) of 477 study participants’ residential addresses to the nearest facility and evaluated whether serum levels varied by proximity. Our results suggested that living within 10 km of solid waste facilities/landfills may be related to higher serum levels of two specific congeners of PBDEs (BDE-47 and BDE-100). During this past year, we also have coordinated the shipment of 898 blood samples collected from the parent CTS study to our environmental chemistry lab. Due to the lower than expected incidence of breast cancer in the CTS cohort, case accrual for our study has lagged behind our study’s original timeline. Consequently, we have modified our study protocol to include 500 stored blood samples previously collected from CTS members to augment the on-going biospecimen collection from prospectively-identified cases. During the current reporting period, we have conducted 2,282 bioassays among study participants who are potentially eligible for our risk analyses (aim#2), including 1,207 for PBDEs, 75 for PCBs/OCPs, and 1,000 for PFCs. To address our third specific aim, we have completed linkages to California birth records and have abstracted residential addresses upon which we are currently working to construct a residential history that will be used to inform potential environmental exposures during early reproductive life. We also have completed linkages to California Department of Education Employment records to build a similar history for workplace locations.

Work in the upcoming year of this project will focus on finalizing and disseminating the results from our Aim #1 analyses, obtaining the stored blood samples from the CTS, conducting the bioassays on these and the remaining prospectively-collected blood samples, completing the construction of workplace and residential histories for study participants, and initiating the construction of our analytic datasets upon which the statistical analyses for our second and third study aims will be conducted.

Publications:
Association between Serum Polybrominated Diphenylether Levels and Residential Proximity to Solid Waste Facilities




Progress Report 6 (2016)

Persistent organic pollutants (POPs) are a large and diverse group of pervasive environmental contaminants of concern for breast cancer risk due to their highly toxic properties and ability to disrupt the endocrine system. The primary aim of this study is to investigate the risk of breast cancer associated with body burden levels of POPs (including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and perfluoroalkyl and polyfluoroalkyl substances (PFASs)) among participants in the California Teachers Study (CTS), a large on-going cohort study of breast cancer among 133,479 female California professional school employees. Ancillary to this main objective is identification of disparities in, and predictors of, body burden levels of these compounds and the exploration of potentially important windows of susceptibility.

During this past year, we focused our efforts on completing the laboratory analyses to measure POPs in the blood of all eligible study participants, including 902 women diagnosed with invasive breast cancer and 1,257 cancer-free controls. While the number of participants is slightly less than our original projections, we will still have ample statistical power to detect risks, if they exist. Initial analyses of these data indicate levels and frequency of detection generally similar to those reported in other studies and national biomonitoring data. These data will now serve as the basis for evaluating whether the levels of POPs measured in blood differ between participants with and without breast cancer. We currently are working to develop statistical models that appropriately take into account potential temporal trends in the data, address multi-pollutant exposures, and adjust for other factors that might influence body burden levels and risk. We anticipate completion of these risk analyses within the next year.

Towards our aim of evaluating potentially important windows of susceptibility, we have created extended residential histories for CTS participants through a variety of linkages to external address data. We are now currently searching for relevant historical georeferenced exposure data that could be used in conjunction with these residential histories to characterize POPs exposures earlier in life.

Our analyses of disparities in, and predictors, of exposure are complete. While few sociodemographic or indoor correlates of exposure were identified, our analyses identified both residential proximity to solid waste sites and drinking water as potentially important routes of exposure to PBDEs and PFASs, respectively. These published findings may have important implications for identifying avenues to mitigate exposures.

During the final year of this project our primary focus will be to complete the breast cancer risk analyses. We also will continue to identify and pursue methodologic analyses relevant to future studies and apply for additional funding to extend our understanding of how these compounds may affect the development of breast cancer, building on the knowledge gained and questions invoked by the current project.




Progress Report 6 (2017)

Persistent organic pollutants (POPs) are a large and diverse group of pervasive environmental contaminants of concern for breast cancer risk due to their toxic properties and ability to disrupt the endocrine system. The primary aim of this study is to investigate the risk of breast cancer associated with body burden levels of POPs (including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and perfluoroalkyl and polyfluoroalkyl substances (PFASs)) among participants in the California Teachers Study (CTS), a large on-going cohort study of breast cancer among 133,479 female California professional school employees. Ancillary to this main objective is identification of disparities in, and predictors of, body burden levels of these compounds and the exploration of potentially important windows of susceptibility.

In seeking to identify predictors and disparities in exposure to these compounds, we have conducted a number of analyses among the cancer-free controls in our study that have yielded results with important public health implications. Two geographic-based analyses identified previously unrecognized sources of exposure – residential proximity to solid waste sites and drinking water contamination – as potentially important routes of exposure to PBDEs and PFASs, respectively. Furthermore, our temporal analysis of PBDE serum levels indicated modest, but statistically significant, increases in the serum concentrations of the three most common PBDEs over the four years of blood collection – despite the ban of these chemicals several years prior to the initiation of the study. These findings are in contrast to a number of other earlier studies that indicated declines in body burden levels shortly after these compounds were banned. Our more recent findings may suggest a shifting towards diet as a major exposure route for PBDEs. In contrast, a similar temporal analysis of PFAS levels among non-cases found average annual declines of about 10-20% over the course of the study, suggesting recent bans in those compounds may be effective in reducing exposures. This set of analyses also highlighted disparites in exposure and rates of change in body burden levels associated with age, suggesting comparative differences in the relative importance of differenct exposures routes by age and/or possible age-related differences in the metabolisim and excretion of these compounds. These results underscore the importance of considering age when developing targeted avenues for reducing exposures and in understanding health-related risks.

After considerable delays earlier in the project, we have now completed the laboratory analyses to measure all targeted POPs compounds in the blood from approximately 900 women diagnosed with invasive breast cancer and 1,250 cancer-free controls. Initial analyses of these data indicate levels and frequency of detection generally similar to those reported in other studies and national biomonitoring data. While the number of participants is slightly less than our original projections, we will have ample statistical power to detect risks, if they exist. These data will now serve as the basis for evaluating whether the levels of POPs measured in blood differ between participants with and without breast cancer. We are currently developing statistical models that optimally account for the temporal trends in the data, appropriately model levels below the limit of detection, address multi-pollutant exposures, and adjust for other factors that might influence body burden levels and risk. We anticipate completion of these breast cancer risk analyses within the next year.Towards our aim of evaluating potentially important windows of susceptibility, we have created extended residential histories for CTS participants through a variety of linkages to external address data that have resulted in the identification of where more than 25,000 study participants lived when they gave birth to a child in California as well as another 25,000 addresses that capture where women lived prior to enrolling in the study. These efforts have effectively doubled the proportion of the CTS for whom we have an address during the childbearing years – a potentially important window of susceptibility to exposures to POPs. Building on some of our earlier analyses, we now plan to conduct a breast cancer risk analysis among parous women that evaluates whether risk of breast cancer is elevated among those who lived in close proximity to a solid waste site at the time they gave birth to their children.




Conference Abstract (2016)

Association between Serum PBDE Levels and Residential Proximity to Solid Waste Facilities/Landfills or Toxics Release Facilities

Ruiling Liu1, David O. Nelson1, Susan Hurley1, Myrto Petreas2, Yunzhu Wang2, Tan Guo2, June-Soo Park2, Pamela Horn-Ross1, Leslie Bernstein3, Hoda Anton-Culver4, Andrew Hertz1, Peggy Reynolds1,5
1Cancer Prevention Institute of California; 2 California Department of Toxic Substances Control; 3Beckman Research Institute of the City of Hope, Department of Population Sciences; 4University of California Irvine, School of Medicine; 5Stanford University School of Medicine, Department of Health Research and Policy

Polybrominated diphenyl ethers (PBDEs), chemicals commonly used as flame retardants, have been the source of some concern for a variety of health outcomes including breast cancer. Some studies have examined the relationship between characteristics of indoor environments and human PBDE body burden, but relatively few have considered the role of outdoor environments as potential exposure sources. We examined the association between serum PBDE levels in California women and residential proximity to solid waste facilities/landfills or toxics release facilities, which may release PBDEs into the environment. 481 participants (median age=66 years; range 40-94 years) from the California Teachers Study provided blood samples in 2011-2013, which were assayed for 19 PBDE congeners via Gas Chromatography/High Resolution Mass Spectrometry DFS. Information on solid waste facilities/landfills was obtained from the California Solid Waste Information System, and for toxics release facilities from the U.S. Environmental Protection Agency Toxics Release Inventory program. Facilities with potential for release of flame-retardants were identified and geocoded, and the distance to each participant’s residential address at time of blood draw was computed. Linear regression was used to examine the association between the proximity to those facilities and the serum levels of three most common PBDE congeners (BDE-47, -100 and -153), adjusting for age, race, body mass index and neighborhood (block group) socioeconomic status. Serum PBDE levels were lipid adjusted (ng/g lipid) and log-transformed for analysis. Subjects living within 10km (n=452) from any solid waste facility/landfill had approximately 45% higher serum BDE-47 levels than those living beyond 10km (p=0.04). Dose response was evident for residences within 3-9 km. Similar associations were not observed for BDE-100 or 153, or for proximity to toxics release facilities. Living within 10km of some solid waste facilities/landfills may be related to higher serum BDE-47 levels. More studies are needed to examine potential exposure routes. Acknowledgements: Funded by CBCRP grant #16ZB-8501.




Conference Abstract (2016)

Comparison of GC-HRMS and GC-MS/MS Methods for the Determination of Persistent Organic Pollutants in Human Serum

S.M.Crispo Smith1; Y Wang2; W Guo2; M. Petreas2; D. Nelson3; P. Reynolds3,4; R. Liu3; S. Hurley3; J-S. Park2
1Sequoia Foundation, La Jolla, CA
2California Department of Toxic Substance Control, Berkeley, CA
3Cancer Prevention Institute of California, Fremont, CA
4Division of Epidemiology, Department of Health Research and Policy, Stanford University School of Medicine, Stanford, CA

Serum analysis of persistent organic pollutants including polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and polybrominated diphenyl ethers (PBDEs), are routinely performed for California Biomonitoring studies, such as the California Teacher’s Study. The California Teacher’s Study measures levels of persistent organic pollutants in California teachers and administrators serum samples collected from 2011 to present, in an effort to establish links between breast cancer and pollutants. Serum samples are extracted using an automated solid-phase extraction system. The sample extracts required separate injections for PCBs/OCPs and PBDEs on two different columns (a 60m SGE HT8-PCB and a 15m Agilent DB-5ms, respectively) installed on gas chromatograph/high resolution mass spectrometer (GC–HRMS, ThermoFisher, Bremen, Germany). A method for the simultaneous determination of 15 PCBs (-66,-74,-99,-101,-105,-118,-138,-153,-156,-170 -180,-183,-187,-194,-203), 7 OCPs (hexachlorobenzene, b-hexachlorocyclohexane, o,p’-DDT, p,p’-DDT, p,p’-DDE, oxychlordane, and trans-nonachlor), and 5 PBDEs (-47,-99,-100,-153,-154) was developed using gas chromatography/triple-quadrupole tandem mass spectrometry (GC-MS/MS, Agilent, Santa Clara, CA) equipped with a 30m DB-5ms column (Agilent). The method was confirmed using samples from the Arctic Monitoring and Assessment Program. The ease of use, 24 minute run time, and low cost of maintenance made this new method attractive for the projects requiring high throughput, like California Biomonitoring projects. Serum data (n=47 for PCB/OCP and n=297 for BDE) produced from GC-HRMS and GC-MS/MS analysis were compared to determine feasibility of using the GC-MS/MS method as an alternative for these large studies. Sample concentrations were determined using average response factors for the GC-HRMS method while calibration curve interpolation was used for the GC-MS/MS method. Most compounds of interest showed linear relationships in the results between the GC-HRMS and GC-MS/MS with slopes of 1.0 ± 0.2 and Pearson’s r values > 0.9, indicating both methods to be generally comparable. However, BDE-47 by the GC-MS/MS method was underestimated by 25%, particularly at high concentrations. The cause of this discrepancy is under investigation. Meanwhile, the issue with BDE-47 was resolved by calculating concentrations using average response factors for the GC-MS/MS method. Our new method improves our throughput and will provide benefits to large cohort studies in the California Biomonitoring Program.

Disclaimer: The views expressed herein are those of the authors and do not necessarily reflect those of the California Department of Toxic Substances Control.