A pilot study was conducted in October 2007 at a large dairy in Yolo County. The objective was to test protocols, equipment, and train staff. No samples were analyzed.
In March 2008 a large winter component study was carried out at a dairy with over 3,000 lactating cows in Fresno County.
Fifteen subjects were monitored over their work shift; six were tested twice to give an estimation of variability. Extensive personal and ambient air sampling was conducted; particle filters and other materials collected have been or shortly will be tested for particle mass, endotoxin content, bioaerosol composition and ammonia levels (as appropriate).
Main Summer Study 2008
The study took place between the last week in June and ended with the third week of September 2008. Thirteen large dairies in California's Central Valley and a control facility in Santa Clara county participated in the study. A total of 224 male dairy workers wore the backpack supporting air sampling equipment while they worked and completed pre- and post-shift questionnaires and breathing tests for one day each. In addition, 49 male employees of a food processing plant (the control facility) completed a similar one-shift monitoring of their personal exposures to airborne materials, breathing changes and were asked pre- and post-shift surveys.
97.8% of the dairy and 97.7% of processing plant employees (controls), were Hispanic. 20.5% of dairy workers and 13.6% of control facility employees were current smokers; the difference in proportions was not statistically significant. Mean age was 33 years (SD=10.8; range 18 - 70) and 36 years (SD=12.2; range 19 - 63) for dairy and control participants, respectively.
In total, 552 filters were collected from personal sampling and 410 filters from area sampling. Of these totals, for the personal sampling, approximately 50% of the filters were material collected from the button samplers (full particle range in size), and 50% from cyclone filters (PM 2.5). The split between button and cyclone samplers was similar for the area sampling.
Other exposure data collected included:
TEOM electronic data flows giving continuous real-time PM 2.5 concentrations was collected from 8 dairies. A Burkard was used to collect bioaerosols from 3 dairies which will be analyzed for allergens and other biological particles. At five of the dairies samples of total particulates fractionated into 4 size fractions from a HiVol were collected. This material will be used to assess the inflammatory potential of the dairy particulates.
The data collected over the main summer sampling is being entered into a web-based database. We will soon download the data sets into permanent SAS databases and begin the process of cleaning the data. All the total suspended solid samples sent for Recombinant factor C (rFC) assay for measuring endotoxin have been analyzed. Samples collected by cyclone sampling are yet to be analyzed by the rFC method. Samples sent for GC/MS analysis of endotoxin are being processed, and we have tested the assay for macrophage inflammatory markers with material collected from one of the dairies.