The Healthy Dairy Worker Study

Dairy workers are commonly exposed to microbes and allergens on the job. However, little is known about whether these exposures provide health benefits or contribute to an increased risk of illness. The ‘hygiene hypothesis,’ suggests that exposure to microbes on farms may have immune benefits.

Project Overview

Our study evaluates the impact of these factors on respiratory and gut health by measuring the nasal and gut bacteria present in the body and comparing it to respiratory function of workers. We will analyze changes in the microbiome and health status for newly hired dairy workers, existing dairy workers, and community members over a two-year period. Our goal is to determine if the quantity and type of bacteria in the microbiome of workers are related to the participant’s health or leaving the job.

Findings to Date

This project completed sample collection in 2022 and has further analysis underway. See ‘Next Steps’ below.

  • Dairy workers performed better on breathing tests and had an abundance of certain ‘healthy’ bacteria that protect against inflammation, as compared to community members. This benefit may be from the greater contact with cows.
  • There appear to be differences between individuals in the amount of gut bacteria associated with inflammation.
  • The study found some evidence that some dairy workers were developing an allergy to cow antigens.

Other Accomplishments

Our sample collection ended in 2022, ending a rigorous 5-year field study of recruitment of four farms and enrollment of 53 farmworker participants for biological sampling.

Dr. Pauline Trinh's PhD dissertation entitled "From Metagenomics to Pangenomics: Characterization of Dairy Worker Microbiomes and Development of Novel Statistical Methodology."

Next Steps

Following the close of data collection and our NIOSH funding, PhD Student Jorge Rivera-Gonzalez has continued data analysis and support the development of manuscripts on the following topics:

  1. Compare microbiome diversity and components between workers and controls,
  2. Determine whether microbiome components are associated with health status or early work cessation,
  3. Assess the microbiome in asthmatic vs non-asthmatic study participants,
  4. Change of microbiome diversity over time, and
  5. Determine degree of microbiome sharing between humans and animals.

Based on our experience with the dairy workers, we created a training module for Infection Prevention and Control on Dairy Farms. We will be adapting this for farm audits by the Washington State Dept. of Labor and Industry.


Carmona J, deMarcken M, Trinh P, Frisbie L, Ramirez V, Palmandez P, Vedal S, Sack C, Rabinowitz P. A Cross Sectional Study of Respiratory and Allergy Status in Dairy Workers. J Agromedicine. 2023 Jul;28(3):545-552.

Trinh P, Roberts MC, Rabinowitz PM, Willis AD. Differences in gut metagenomes between dairy workers and community controls: a cross-sectional study. bioRxiv [Preprint]. 2023 May.

Trinh P. From Metagenomics to Pangenomics: Characterization of Dairy Worker Microbiomes and Development of Novel Statistical Methodology. 2022 Doctoral Dissertation. Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, Washington. See Abstract. ResearchWorks.

de Marcken MG. 2020. Occupational Dairy Exposure and IgE-mediated Allergic Disease in Yakima, WA. 2020 Master’s Thesis. Department of Environmental and Occupational Health Sciences, University of Washington. ResearchWorks.

Report: The Healthy Dairy Worker Study 

Partners and Advisories

  • Washington State University, Department of Global Animal Health
  • Washington State Dairy Federation
  • UW Center for One Health Research


Findings as reported at the end of year five are included in our annual report.

Principal Investigator: Peter Rabinowitz, MD, MPH, Associate Professor, Environmental and Occupational Health Sciences, University of Washington

NIOSH Funding Period 2016-2022