Occupational exposure to carbon dioxide, ammonia and hydrogen sulphide on livestock farms in north-west Spain.

The influence of the type of farming on harmful gas exposures to carbon dioxide (CO(2)), ammonia (NH(3)) and hydrogen sulfide (H(2)S) was assessed from the perspective of animal welfare and occupational hygiene. Summer data of H(2)S, NH(3) and CO(2) concentrations and of environmental parameters were collected from 31 farms. The indices of exposure for long-term exposures to NH3 suggest the lowest acceptability of exposure was observed on poultry farms. CO(2) had the highest dependence on production activity. For H(2)S, no differences were found based on farming activity. Both the stocking density and volume of air available affected the daily exposure and the index of exposure to CO(2). Significant differences were observed between hourly CO(2) concentrations, depending on the level of activity inside the building. A positive correlation was found between gas concentrations and temperature increase. All values of daily and short-term exposures were below exposure limit values, which suggests that exposure conditions were appropriate for workers' health during the measurement period. Analysis of the working hours and average hourly concentration of gases during the times of day, with presence of workers inside the farm buildings, revealed significant differences for CO(2).