Ammonia is a naturally occurring, c

Ammonia is a naturally occurring, colourless, acrid-smelling gas. It is volatile and highly water-soluble. On a global scale, more than 99% of the ammonia present in the atmosphere is the result of natural processes. These natural processes consist mainly of biological degradation of organic matter, such as plants and animals, and chemical and microbial degradation of animal wastes, in particular urine. The major sources for atmospheric emissions of ammonia in Alberta would be agricultural activities (animal feedlot operations and other activities), followed by biomass burning (including forest fires) and to a lesser extent fossil fuel combustion (industrial sources) and accidental releases.
Two different types of potential health effects are considered important for ammonia: acute non-cancer effects that may result from short-term exposure and chronic non-cancer effects that may result from long-term exposure. Acute health effects reported in animals following short-term inhalation of ammonia include oral, nasal and eye irritation; respiratory tract irritation; decreased respiratory rate; increased respiratory depth; reduced body weight; and lethargy. These types of effects have been observed in controlled animal studies at concentrations ranging from 50 to 500 mg/m3 (72 to 720 ppm) over exposure durations ranging from 6 hrs (continuously) to 40 hrs (intermittently over 5 days). Similar acute effects of ammonia inhalation are reported for humans (oral, nasal and eye irritation, and respiratory tract irritation) for comparable exposure concentrations and durations.
The health effects following chronic inhalation exposure of animals include nasal irritation; inflammatory response in lungs; reduced olfactory acuity; and lethargy. Animal studies have also demonstrated that ammonia exposure can reduce immune response and increase susceptibility to bacterial infection of the respiratory tract. These types of effects have been observed in controlled animal studies at concentrations ranging from 40 to 1,105 mg/m3 (58 to 1,590 ppm) over exposure durations ranging from 24 to 90 days continuously. Chronic effects reported in humans include reduction in pulmonary function; cough; phlegm; wheeze, and dyspnea. These types of effects have been observed at an estimated exposure concentration equivalent to 50 mg/m3 (72 ppm) over one year of occupational exposure.
Ammonia may affect vegetation directly by influencing the nitrogen cycling in ecosystems. Depending on the sensitivity of vegetation, exposure to ammonia may be harmful to plants. Adverse effects on vegetation occur when the rate of foliar uptake of ammonia is greater than the rate and capacity for in vivo detoxification by the plants. Most to least sensitive plant species are native vegetation, forests, and agricultural crops. The effect on materials from exposure to an individual air pollutant is difficult to separate from the effect of others. Many of the effects on materials have been ascribed more to the multi-pollutant situation that exists in urban environments than to the action of separate pollutants. Ammonia may be contributing to material damage in several ways, but its role is not yet clarified in the scientific literature.
Concentration-response levels in ambient air used for the protection of acute and chronic health effects in humans are on the same order as concentrations used for protecting vegetation. This
Assessment Report on Ammonia for Developing Ambient Air Quality Objectives – Vol. I viii
indicates that human health-based air quality criteria for ammonia may be adequate for protection of vegetation.
The current Alberta Environment 1-hour Ambient Air Quality Guideline for ammonia is 1,400 μg/m3 (2,000 ppb) and based on odour perception. Manitoba Conservation also has a similar guideline and basis for development. The province of Ontario uses a maximum point of impingement guideline of 3,600 μg/m3 (5,184 ppb) for a 30-minute averaging time. Acute ambient air guidelines used by jurisdictions in United States – for the most part – are based on non-cancer risk assessment of irritant effects to the respiratory system in humans.
The Alberta Environment 1-hour guideline appears to be adequate in protecting against reported acute effects of inhalation when compared to other short-term (≤ 24 hours) air quality guidelines developed using non-cancer risk assessment procedures. For example, Alberta Environment’s 1-hour guideline is less than that adopted by state agencies in California (3,200 μg/m3 or 4,600 ppb) and North Carolina (2,700 μg/m3 or 3,900 ppb). State agencies in Ohio and Texas use a 1-hour guideline of 170 μg/m3 (25 ppb) derived from the American Conference of Governmental Industrial Hygienists 8-hour Threshold Limit Value (17,000 μg/m3 or 25 ppm).
Two state agencies, Louisiana and Vermont, use 8-hour guidelines ranging from 640 to 1,800 μg/m3 (920 to 2,590 ppb) for specific purposes. Another four state agencies use 24-hour guidelines rangi