title: Evaluation of the impact of a natural gas leak from a pipeline on productivity of beef cattle.
abstract: OBJECTIVE
  To determine the association between a leak of sour natural gas (more than 30% hydrogen sulfide) from a pipeline in a river valley and the health of beef cattle in the intensively ranched surrounding area.
  
  
  METHODS
  Prospective cohort study.
  
  
  METHODS
  13 herds of cattle within 4 km (2.5 miles) of the leak and 10 herds outside the 4-km zone.
  
  
  METHODS
  Distance of herds from the leak site was determined, using geographic information system technology. Information about speed and direction of winds was obtained from a local meteorologic station and an ambient air-quality monitoring trailer. Health and productivity data for surrounding beef herds, as well as exposure information, were collected and analyzed.
  
  
  RESULTS
  An association was not found between total herd calf mortality and herd distance from the leak, wind-aided exposure, location in the river valley, signs of irritation consistent with exposure to the gas, or reports of odors of gas at the time of the leak. Management changes reported in response to the gas leak were identified as risk factors for total herd calf mortality. Other herd-level risk factors associated with increased calf mortality ratio included a median calving date in February and percentage of twin births for a herd.
  
  
  CONCLUSIONS
  In this example, we did not detect an association between productivity of cattle and exposure to sour natural gas. Several methods can be used for ranking potential exposure after discovery of a leak.
authors.affiliation: Department of Herd Medicine and Theriogenology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada.
authors.forename: C L
authors.initials: CL
authors.lastname: Waldner
authors.forename: C S
authors.initials: CS
authors.lastname: Ribble
authors.forename: E D
authors.initials: ED
authors.lastname: Janzen
mesh_terms: D000034:Abortion, Veterinary / Q000453:epidemiology; D000397:Air Pollution / Q000009:adverse effects*; D000416:Alberta; D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000139:chemically induced* / Q000401:mortality; D015331:Cohort Studies; D004190:Disasters; D005260:Female; D005313:Fetal Death / Q000453:epidemiology / Q000662:veterinary; D005579:Fossil Fuels / Q000009:adverse effects*; D006862:Hydrogen Sulfide / Q000009:adverse effects; D009812:Odorants; D011247:Pregnancy; D011272:Pregnancy, Multiple / Q000706:statistics & numerical data; D011446:Prospective Studies; D012307:Risk Factors; D014887:Weather; D014919:Wind
chemical_list: D005579:Fossil Fuels; D006862:Hydrogen Sulfide