ORIGINAL ABSTRACT

BACKGROUND: Multicentric lymphoma (ML) in dogs has similar clinical features to human non-Hodgkin lymphoma (NHL). NHL has been linked to herbicides and volatile organic compounds (VOCs), direct exposures to these chemicals have not been evaluated in ML. HYPOTHESIS/OBJECTIVES: ML in pet dogs was associated with herbicide and VOC exposures. ANIMALS: Twenty pet boxer dogs with ML and 20 unaffected pet boxer dogs enrolled across the United States between 2021 and 2024. METHODS: Prospective case-control study. Dog owners completed an environmental questionnaire and submitted dog urine, drinking water, and household air samples for analysis of the herbicides 2,4-D, glyphosate, and atrazine and the VOCs benzene, 1,3 butadiene, and trichloroethylene. Area Deprivation Indices (ADI) and USDA Rural-Urban Continuum Codes (RUCC) were assigned to all dogs based on home address. RESULTS: Boxers with ML were more likely to live in more urban counties (median RUCC 1, range 1-6 for cases, vs. median 2, range 1-8 for controls; p = 0.032). Urinary concentrations of the benzene metabolite S-phenylmercapturic acid (PHMA) were higher in dogs with ML (median 1.03 ng/mg creat, range 0.00-1.53) compared to control dogs (0.54 ng/mg creat, range 0.09-4.73; p = 0.031). Odds ratios for exposure to the benzene metabolite MUCA were higher in cases vs. controls, even when controlled for urbanicity (OR 1.01, 95% CI 1.00-1.02; p = 0.035). CONCLUSIONS AND CLINICAL IMPORTANCE: ML in boxers might be associated with benzene exposures. If this association is causative, indoor benzene exposures could be remediated with activated carbon air filtration and certain house plants.