Horses owned by the Thurston family of Edmonton, Alberta, Canada, were exposed to a gas leak from a sour oil facility four months ago, and family members say the livestock still have not recovered, according to an article on canada.com. Sour oil contains the poisonous gas hydrogen sulphide, according to the article.

The horses, used for the family’s sons in their award-winning trick riding act, are listless, have no energy, and have problems with “lung capacity,” the article reported. Cattle on the farm are losing weight. And the family said they are worried about their children, one of whom has asthma that has required additional medication since the exposure.