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Air pollutants: Carbon Monoxide

What is carbon monoxide?

Carbon Monoxide (CO) is an odorless, tasteless and colorless toxic gas, dangerous for humans and wildlife in higher concentrations than 35 ppm. Carbon monoxide composition is made of one carbon atom and one oxygen atom. It plays an important role in smog formation since it can react to create ground-level ozone.

What causes carbon monoxide?

Carbon monoxide is the result of an incomplete burning of organic matter. It is naturally produced in big amounts in the troposphere. Likewise, it can also be generated by volcanoes, forest fires, and other natural combustion processes.

Man-made activities also emit tons of CO, in fact we are the main cause for CO emissions. For example, cars with internal combustion engines and without catalytic converters are huge generators of carbon monoxide. Even if they have catalytic converters, the first 90 seconds after turning on the engine will produce from 10.000 to 30.000 ppm of CO.

Other carbon monoxide human sources are heaters or cooking equipment that runs on carbon-based fuels. These fuels include furnaces, gas ovens, gas water heaters, gas room heaters, kerosene room heaters, charcoal BBQs, portable generators fireplaces, among a lot more.

Carbon monoxide pollution health effects

You go to work and turn on your car’s engine inside your garage. The emissions of CO produced during the ignition will instantly pollute the air you are breathing indoors. Even with the door open, this polluted air will probably reach higher levels than 100 ppm and, as soon as the garage door is closed, it will scatter all over the building.

Indoors and outdoors, breathing high concentrations of CO reduces the amount of oxygen transported in the bloodstream. This can increase the probability of carbon monoxide poisoning in critical organs like the heart or the brain.

Carbon monoxide poisoning: symptoms, treatment and prevention

Carbon monoxide cannot be detected by humans naturally, and special equipment is used to measure it. However, there are a few symptoms that can help you identify carbon monoxide poisoning.

Symptoms are often described as similar to flu. Most common are weakness, headache, dizziness, confusion, chest pain, fatigue, nausea or even death. Long-term exposure to carbon monoxide can produce memory loss, feeling tired or movement problems. Continued and constant CO exposure over the time may cause chronic poisoning, making you feel the mentioned symptoms for life.

Except from extreme cases, carbon monoxide poisoning can be solved just by moving to a non polluted area and breath, instantly pushing the pollutant out and substituting it by oxygen. However, if somebody needs treatment, he will use non-rebreather masks, which administer oxygen. In extreme cases the person can also be placed inside a hyperbaric oxygen chamber.

As mentioned, we cannot detect CO by ourselves without any special equipment. That is why it is important and recommended by governments to install carbon monoxide detectors or alarms at home, used to measure CO levels overtime. These warn in case concentrations are getting dangerous and may cause a public health issue, recommending to evacuate or air out the area.

Effects of carbon monoxide on environment

Carbon monoxide is different from other pollutants since it has not a direct impact on the environment and it can persist over a month in the atmosphere. Although considered a greenhouse gas, it contributes indirectly to climate change. Its presence affects concentrations of other greenhouse gases like methane, tropospheric ozone and carbon dioxide, creating particles and other harmful pollutants.

How is carbon monoxide pollution controlled?

Over the years, developed countries have reached some agreements to control pollution. Each country or state has its own implementation plan. For example, the Clean Air Act made by the U.S. Environmental Protection Agency (EPA) establishes National Ambient Air Quality Standards (NAAQS) for those criteria pollutants considered most harmful for health and the environment. Another example is the European Union Air Quality Directive by the European Environmental Agency, which also establishes some standards and tips to reduce air pollution, both indoors and outdoors.

Since CO is a primary criteria pollutant due to its effects on human health and public safety, maximum permitted or recommended levels for carbon monoxide are:

  • Nothing is included in the World Health Organization (WHO) guidelines.
  • NAAQS: 35 ppm (40 μg/m³) for 1 hour exposure and 9 ppm (10 μg/m³) for 8 hours.
  • EU Air Quality Directive: 10 mg/m³ for a maximum of  8 hour daily exposure.
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