As there are many hazardous gases in our air. Let’s concentrate on the one most harmful to us.
Carbon Monoxide
Carbon monoxide (CO) is a colourless, odorless, and toxic gas released by burning fossil fuels and the biggest polluter are our automobiles, but also the industry and residential furnaces and heaters. Especially when engines are not properly tuned or furnaces not properly maintained and fuel is not completely burned it can emit a high concentration of carbon monoxide.
Carbon monoxide is also often called the “silent killer”. When carbon monoxide is inhaled, it combines with hemoglobin (an iron-protein component of red blood cells), producing carboxyhemoglobin (COHb), which greatly diminishes hemoglobin’s oxygen-carrying capacity. Hemoglobin’s binding affinity for carbon monoxide is 300 times greater than its affinity for oxygen. As a result, small amounts of carbon monoxide can dramatically reduce hemoglobin’s ability to transport oxygen. Common symptoms of carbon monoxide exposure are headache, nausea, rapid breathing, weakness, exhaustion, dizziness, and confusion. Hypoxia (severe oxygen deficiency) due to acute carbon monoxide poisoning may result in reversible neurological effects, or it may result in long-term (and possibly delayed) irreversible neurological (brain damage) or cardio-logical (heart damage) effects.
CO maximum exposure for humans is set to 10 mg/m3 in a daily 8 hour mean
Nitrogen Oxides
Nitrogen oxide (NOx) is a generic term for the various nitrogen oxides produced during combustion. While all of these gases are harmful to human health and the environment, NO2 is of greater concern.
Nitrogen dioxide (NO2) is primarily emits in the air from the burning or fossil fuels by power plants and automobiles.
Nitrogen dioxide is formed in two different ways:
- direct when fossil fuel is burned, or
- when, nitrogen in the air reacts with oxygen.
Nitrogen dioxide can also react in the atmosphere to form ozone, acid rain, and particles.
Breathing air with a high concentration of NO2 can irritate airways in the human respiratory system. Such exposures over short periods can aggravate respiratory diseases, particularly asthma, leading to respiratory symptoms (such as coughing, wheezing or difficulty breathing), hospital admissions and visits to emergency rooms. Longer exposures to elevated concentrations of NO2 may contribute to the development of asthma and potentially increase susceptibility to respiratory infections.
NO2 maximum exposure for humans is set to 40 µg/m3/annual while a max of 200 µg/m3 per hour should not be crossed, while the European Law the hourly max should not be exceeded more than 18 times a year.
Sulfur Oxides
particularly Sulfur dioxide (SO2) is a gas. It is invisible and has a nasty, sharp smell. It reacts easily with other substances to form harmful compounds, such as sulfuric acid, sulfurous acid and sulfate particles. About 99% of the sulfur dioxide in air comes from human sources, mostly comes from burning of fossil fuel (mainly coal and oil) in power plants, but it also comes from factories producing chemicals, paper or fuel.
During the process of oxidation in the atmosphere this gas forms sulfates or salts that can be transported in the breathable particulate material (PM10) that in presence of humidity forms acids. Later these acids are an important part of the secondary particulate material or finest particulate material (PM2,5). The exposure to sulfates and the exposure to acids derived from SO2 is extremely risky for people’s health because these compounds enter the circulatory system directly through the airways.
The SO2 is hydroscopic, when it is in the atmosphere it reacts with humidity and forms sulfuric and sulfurous aerosol acid that is later part of the so-called acid rain. The intensity in the formation of aerosols and the permanence of them in the atmosphere depend on the meteorological conditions and the quantity of catalytic impurities (substances that accelerate the processes) present in the air. But in general, the average time of permanence in the atmosphere is around 3-5 days, so it can be transported to greater distances.
The air pollution by SO2 has the following effects on human beings:
Breathing difficulty, Airways inflammation, Eye irritation, Psychic alterations, Pulmonary oedema, Heart failure, or Circulatory collapse.
SO2 maximum exposure for humans is set to 125 µg/m3/day while a max of 350 µg/m3 per 1 hour should not be crossed
Ammonia
Ammonia (NH3) is emitted from agricultural processes and fertilizer production. It is normally encountered as a gas with a characteristic pungent odor. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to foodstuffs and fertilizers. Ammonia, either directly or indirectly, is also a building block for the synthesis of many pharmaceuticals.
Although in wide use, ammonia is both caustic and hazardous. In the atmosphere, ammonia reacts with oxides of nitrogen and sulfur to form secondary particles. Exposure to high concentrations of ammonia in air causes immediate burning of the nose, throat and respiratory tract. This can cause bronchiolar and alveolar edema, and airway destruction resulting in respiratory distress or failure. Inhalation of lower concentrations can cause coughing, and nose and throat irritation.
It combines in the atmosphere with sulfates and nitrates to form secondary fine particulate matter (PM2.5). PM2.5 is known to have harmful effects on human health and the environment.
In Europe the emissions of NH3 are regulated, but the regulations and measurements are not very effective and we are far away of setting reliable targets. In Europe Ammonia readings are not part of the AQI (Air Quality Index), but for example in India it is part of the AQI.
But all these gases do not have only an effect on nature by causing acid rain, they have also a direct negative health effect on us humans.
- CO (carbon monoxide) combines with hemoglobin to lessen the amount of oxygen entering our blood through our lungs. The binding with other haeme proteins causes changes in the function of the affected organs such as the brain and the cardiovascular system, and also the developing fetus. It can impair our concentration, slow our reflexes, and make us confused and sleepy.
- NOx (nitrogen oxides) makes children susceptible to respiratory diseases
- SO2 (sulfur dioxides) in the air leads to diseases of the lung and other lung disorders such as wheezing and shortness of breath. Long-term effects are more difficult to ascertain as SO2 exposure is often combined with that of particulate matter.