Page 702 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

Petroleum Chapter | 50 667

VetBooks.ir pipeline breaks and to prevent exposure to H 2 Sduring set on fire and the emissions are a complex mixture of
products of combustion and PIC. In the blowout incidents,
uncontrolled releases (blowouts). The toxicology of sour
which have been reported in the literature, cattle were
petroleum is often indexed on the toxicology of H 2 Sfor
well emissions and on sulfur dioxide (SO 2 ) for products of confined by fences, corrals, etc., and generally could not
combustion from burning sour petroleum. These assump- escape the air-borne emissions. Ranchers and their fami-
tions ignore the toxicology of a complex chemical mixture. lies generally have been forced to evacuate the danger
Sour gas is crude natural gas that contains H 2 S and area leaving cattle and other livestock unattended or were
other sulfur compounds (Coppock and Christian, 2012). not allowed to attend to livestock confined in the cor-
Uncontrolled releases of sour gas constitute a unique haz- doned off area. These events can cause major disruptions
ard to humans and other animals. Uncontrolled release of in basic animal husbandry. Sour gas is heavier than air
6
3
sour gas into the environment can be 4.2 3 10 m /day and settles into low areas especially during cool tempera-
and the release of sulfur compounds equivalent to tures. Low areas tend to be sheltered from the wind and
900 1400 metric tons of elemental sulfur/day. The gas less dilution of the sour gas occurs. The toxic effects of
well emissions from uncontrolled releases are a complex sour gas have been summarized in Table 50.2. Livestock
mixture of chemicals generally containing condensate, exposed to sour gas do not have clinical signs that are
produced water and other substances. The wells may be uniquely different from infectious diseases.

TABLE 50.2 Summary of Observed Effects of Gaseous Petroleum Emissions in Cattle
Incident Observation References
Canada Watery discharge from eyes and nostrils. Post exposure pneumonia was observed EPS (1973)
Canada, Lodgepole Ocular and respiratory irritation, abortions, other reproductive problems Round (1992)
Blowout
Number of aborted fetuses and diagnostic trends did not change for the Provincial Klavano and
Laboratory (Edmonton) during and after the blowout Christian (1992)
Maladies in cattle increased with decreasing distance from the well and were increased Harris (1992)
in geographically low areas. Maladies associated with trace mineral deficiency were
observed. Other maladies observed were changes in hair color, inertia uteri, calves born
with deformed feet, failure to thrive following birth, decreased growth of replacement
heifers, and 20% reduction in milk production by dairy cows, increased calving
interval. Herds returned to pre- exposure level of health problems
Significant reduction in weaning weights of calves that were exposed as cow-calf pairs Whitelock (1992)
The conclusions from this study were: physical examinations were within the expected Church (1992)
normal variation, pathological findings were of varied diagnosis, and were not
considered to be unique, three calves from these cows raised at the laboratory grew at
average to above-average rates, parameters used may not have been sensitive enough to
detect irreversible toxicological effects, and the owner may have been biased in his
evaluation of long-term effects
Mississippi (USA) Post exposure observations were irritation of the eyes and respiratory tract, respiratory Edwards (1992)
distress, and intolerance to exercise
Canada Clinical signs mimicked shipping fever, but infective agents or clinical evidence of Anon (1986)
infection were not detected, exposed feedlot cattle had extended feeding time to finish,
loss of stamina in cattle, exercise intolerance in horses, exposure to sour gas may have
contributed to shipping fever in recently weaned calves, and claims of reproductive
failures were not established
Canada, multiphase Observed effects were ocular and nasal irritation, evidence of immune and nervous Mostrom and
pipeline leak system dysfunction, abnormal aggressive behavior in cows, in estrus behavior of Campbell (1996)
pregnant cows, above average mortalities in cows and calves, calves lacked sucking
instinct, cows failed to nurture new born calves, and lesions in lymph nodes and
trachea