ves, and other basic demographic and health data were also obtained. Individuals with prior histories of lymphoproliferative malignancies (such as multiple myeloma or lymphoma) were excluded. Cancer incidence and mortality were monitored annually, and, after five years, follow-up interviews were conducted to update the information about participants' occupational exposures, medical histories, and lifestyle factors.
For comparison, data were obtained from a large MGUS-screening study conducted by the Mayo Clinic, and the results from the pesticide-exposed group were compared with the assessments of 9,469 men from the general population of Olmsted County, Minnesota. The two groups were similar in terms of age, race, and educational attainment. Because of the low prevalence of women among workers who apply pesticides, women were excluded from the study.
In the pesticide-exposed group, no MGUS cases were observed among those who were less than 50 years of age, but the prevalence of MGUS in those older than 50 was 6.8 percent, which is 1.9 times higher than the general population study group of men in Minnesota.
The researchers also evaluated the potential association between MGUS prevalence and 50 specific pesticides for which usage data were known. Of the chemicals studied, a significantly increased risk of MGUS was observed among users of dieldrin (an insecticide), carbon-tetrachloride/carbon disulfide (a fumigant mixture), and chlorothalonil (a fungicide). The MGUS risk for these agents increased 5.6-fold, 3.9-fold, and 2.4-fold, respectively. Several other insecticides, herbicides, and fungicides were associated with MGUS, but not significantly.
"There is great concern regarding the increase in frequency in mature B-cell malignancies in the Western world and what may be the cause of this. A number of reports in the past have linked exposure to pesticides with increased risk of these types of cancers, but the present study is the first to link agricultural work to a pre-malignant condition," said John G. Gribben, MD, DSc, Professor of Experimental Cancer Medicine at Barts and the London School of Medicine, who is not affiliated with the study. "It is vital to assess the risk of workplace exposure and disease, and the results lend further support to providing safe workplace practices to limit exposure to potential carcinogens."
"Our findings are intriguing," stated Dr. Landgren. If replicated in a larger sample from our study and other large studies, further work should focus on gaining a better understanding of the molecular basis of MGUS and multiple myeloma. Ultimately, this will result in the identification of novel molecular targets involved in the progression from MGUS to multiple myeloma and in the development of targeted therapies."
Source: American Society of Hematology
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