Laura Beane Freeman, Ph.D.
|Organization:||National Cancer InstituteDivision of Cancer Epidemiology & Genetics, Occupational and Environmental Epidemiology Branch|
|Address:||Executive Plaza SouthRoom 8112|
Dr. Beane Freeman completed her doctorate in epidemiology at the University of Iowa in 2003, after which she joined the Cancer Prevention Fellowship Program at NCI. Dr. Beane Freeman conducted her post-doctoral training within the Occupational and Environmental Epidemiology Branch where she became a Research Fellow in 2006. In 2009, Dr. Beane Freeman was appointed to the position of tenure-track investigator. Her research has been recognized with Fellows Awards for Research Excellence from both the National Institutes of Health and the Division of Cancer Epidemiology and Genetics.
Our research involves the design and conduct of epidemiologic investigations to evaluate environmental and host determinants of cancer. We closely monitor new findings from clinical observations, experimental studies, and descriptive and analytic epidemiology for leads as to causes of cancer. My research focuses particularly on the etiology of lymphohematopoietic cancers and the effects of agricultural exposures on cancer risk.
Studies around the world have observed that farmers and other agricultural workers are at elevated risk of several specific cancers, despite lower overall mortality and, in particular, cancer mortality. In this occupational group, excess risks are observed for Hodgkin lymphoma, non Hodgkin lymphoma, leukemia, multiple myeloma, and cancers of the brain, skin, lip, stomach, and prostate. Work-related exposures suspected of contributing to the excesses include pesticides, sunlight, viruses, mycotoxins, well-water contaminants, and a variety of other agents encountered in the agricultural environment.
In collaboration with investigators at the National Institute of Environmental Health Sciences, the National Institute for Occupational Safety and Health, and the Environmental Protection Agency, we are conducting the Agricultural Health Study (AHS) to evaluate exposures that may be responsible for the cancer excesses. This prospective cohort study of about 90,000 participants includes licensed private pesticide applicators, their spouses, and commercial pesticide applicators. We are following this cohort to collect data on cancer incidence and mortality. Our work in the AHS has shown that pesticides such as organophosphate compounds may be associated with different cancer risks. Diazinon has been associated with leukemia and lung cancer but malathion, another organothiophosphate with a similar chemical structure, showed no such associations. Within the AHS, we are also investigating whether exposure to animals through delivery of veterinary services increases cancer risk, as some evidence points to blood-borne pathogens as the reason for increased risk of NHL.
Another important exposure is endotoxin and other pathogen-associated molecular patterns (PAMPs). Workers in other occupations with high endotoxin exposures, such as those in cotton textile industries, have a decreased risk of lung cancer. We are examining whether the deficit of lung cancer in the AHS may be partially explained by endotoxin exposure.
In 2004, the International Agency for Research on Cancer (IARC) upgraded formaldehyde from a probable to a known human carcinogen, based primarily on its association with nasopharyngeal cancer. However, without an identified mechanism for leukemogenicity, IARC ruled there was strong, but not sufficient evidence for an association with leukemia, particularly myeloid leukemia. The NCI Cohort of Workers in Formaldehyde Industries is the largest study of occupationally exposed workers and includes over 25,000 participants who have median follow-up time of over forty-years. Results from earlier updates of this study played an important role in IARC’s decision to reclassify formaldehyde, but conflict with results from another large cohort study with respect to leukemia. Our recent follow up on this study added another ten years of mortality data, allowing us sufficient person years to explore effects at different time periods and offered further insight into temporality of potential associations between formaldehyde and leukemia and other lymphohematopoietic malignancies.
Arsenic has been implicated in the development of a number of cancers, but most studies have focused on populations exposed at very high levels. Studies in Taiwan, Argentina and Chile have shown increased risk of bladder cancer with ingestion of high levels of arsenic. Less clear is the potential association between lower levels of arsenic exposure and cancer risk. Within a large case-control study, NCI investigators are developing a comprehensive arsenic exposure assessment. We are utilizing data on arsenic in drinking water from a variety of sources and the exposure assessment will be used to investigate the association between relatively low levels of arsenic exposure and bladder cancer.
Results from previous studies indicate that exposure to disinfection by-products (DBPs) also increases risk of bladder cancer. Recent results from a case-control study in Spain suggest that in addition to ingestion, exposure through showering and bathing may contribute to risk. Using detailed exposure assessment methods, we aim to perform etiologic analyses of disinfection by-products to investigate whether these results can be replicated within a large case-control study within the US.