A prospective field study examining the association between environmental emissions from the petroleum industry and the productivity of commercial beef cows

The health and productivity of seven cow-calf herds located near a new sour gas processing plant was measured using newly developed intensive biological accounting methods. Production records from more than 7000 bull contacts were examined from 1991 to 1997. Detailed information was collected on other risk factors which could influence beef herd productivity. Published reports were in good agreement with the collected data on the median risks for non-pregnancy, abortion, late calving, stillbirth, calf mortality, calving date or weaning weight. Herd age-adjusted weight for both male and female calves improved significantly. Exposure assessments made on individual animals indicated that there is no consistent association between the total sulfation and H2S deposition which was used as markers for the compounds found in emissions from sour gas processing plants and flares. However, five examples of association were found to exist between increasing exposure to total sulfation and decreased productivity. Finally, the association between cow-calf productivity and cumulative animal proximity to petroleum field facilities and sour gas flares from battery sites was examined. It was determined that an increased risk of non-pregnancy was sometimes associated with exposure to sour flaring, battery facilities, active gas wells and larger field facilities, but the association was not consistent from from year to year. Flaring was not found to be associated with increased abortion risk, but volume of flared sour gas from battery sites was associated with an increased risk of stillbirth. In the 1992-1993 calf crop, sour flaring was found to be associated with an increased risk in calf mortality