Cows as canaries: The effects of ambient air pollution exposure on milk production and somatic cell count in dairy cows

Bonni L Beaupied; Heather Martinez; Sheena Martenies; Craig S McConnel; Ilana B Pollack; Dylan Giardina; Emily V Fischer; Shantanu Jathar; Colleen G Duncan; Sheryl Magzamen

doi:10.1016/j.envres.2021.112197

Cows as canaries: The effects of ambient air pollution exposure on milk production and somatic cell count in dairy cows

Environ Res. 2022 May 1:207:112197. doi: 10.1016/j.envres.2021.112197. Epub 2021 Oct 23.

Authors

Affiliations

¹ Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO, USA.
² College of Veterinary Medicine, Washington State University, Pullman, WA, USA.
³ Department of Atmospheric Science, Colorado State University, Fort Collins, CO, USA.
⁴ Department of Mechanical Engineering, Colorado State University, Fort Collins, CO, USA.
⁵ Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO, USA.
⁶ Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO, USA. Electronic address: sheryl.magzamen@colostate.edu.

PMID: 34699758
DOI: 10.1016/j.envres.2021.112197

Abstract

Exposure to air pollution, including criteria pollutants such as fine particulate matter (PM_2.5) and ozone (O₃), has been associated with morbidity and mortality in mammals. As a genetically homogenous population that is closely monitored for health, dairy cattle present a unique opportunity to assess the association between changes in air pollution and mammalian health. Milk yield decreases in the summer if temperature and humidity, measured by the Temperature Humidity Index (THI). As O₃ levels increase with warmer temperatures, and summer PM_2.5 may increase with wildfire smoke, dairy cows may serve as a useful sentinel species to evaluate subacute markers of inflammation and metabolic output and ambient pollution. Over two years, we assessed summertime O₃ and PM_2.5 concentrations from local US EPA air quality monitors into an auto-regressive mixed model of the association between THI and daily milk production data and bulk tank somatic cell count (SCC). In unadjusted models, a 10 unit increase THI was associated with 28,700 cells/mL (95% CI: 17,700, 39,690) increase in SCC. After controlling for ambient air pollutants, THI was associated with a 14,500 SCC increase (95% CI: 3,400, 25,680), a 48% decrease in effect compared to the crude model. Further, in fully adjusted models, PM_2.5 was associated with a 105,500 cells/mL (95% CI: 90,030, 121,050) increase in SCC. Similar results were found for milk production. Results were amplified when high PM_2.5 days (95th percentile of observed values) associated with wildfire smoke were removed from the analyses. Our results support the hypothesis that PM_2.5 confounds the relationships between THI and milk yield and somatic cell count. The results of this study can be used to inform strategies for intervention to mitigate these impacts at the dairy level and potentially contribute to a model where production animals can act as air quality sentinels.

Keywords: Air pollution; Dairy cattle; Environment; Epidemiology; Fine particulate matter; Ozone.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Air Pollutants* / analysis
Air Pollutants* / toxicity
Air Pollution* / adverse effects
Air Pollution* / analysis
Animals
Canaries
Cattle
Cell Count / veterinary
Female
Mammals
Milk / chemistry
Particulate Matter / analysis
Particulate Matter / toxicity

Substances

Air Pollutants
Particulate Matter