A study of lichens in the Côtes d'Armor region has revealed that lichen flora has adapted to the presence of nitrogen compounds (ammonia) in the atmosphere. Since ammonia is known to be an irritant gas, this research raised questions in the studied region about the potential impact of ammonia emissions on the health of populations living in areas of intensive livestock farming. It was in this context that the objective was set to assess the risk associated with atmospheric ammonia levels for individuals not occupationally exposed. The identification of the substance’s hazard potential and the determination of the probability of the hazard occurring were carried out through a literature review. This study showed that measured and modeled exposure levels remain below the values recommended for health protection, and it is possible, given the existence of a threshold, to conclude that atmospheric ammonia should not cause irritation in the population.