Air pollution

What is carbon monoxide?

By Yoki Ho

Carbon monoxide (CO) is a colourless, odourless and tasteless gas which is a by-product from incomplete combustion of any fuel which contains carbon, such as gasoline, wood and natural gas. You cannot smell, see or taste CO, but CO can be lethal! You do not need a high concentration of CO to experience its health impacts, as little as 0.4% concentration of CO in the air around us can result in unconsciousness and death in just a few minutes. This is because CO is absorbed through the lungs and transported by bloodstream to enter the body cells.  The oxygen carrying capacity of red blood cells in blood is affected. Furthermore, it prohibits the release of energy inside cells by utilizing oxygen. What happens next? Ome experiences hypoxic effects and damage to essential body organs, the brain and the heart in particular. Be careful if you find yourself feeling dizzy and fatigued in the outdoors, there is a chance that you have inhaled a low concentration of carbon monoxide.

Did you know that CO poisoning may not be accidental but intentional? Sadly, it accounts for a number of suicidal cases and other death cases every year. While some cases cannot be tackled by air quality control measures, we can still spread the message of the prevention of accidental CO poisoning through public education. As a student living in Hong Kong, I am well aware of the congested traffic and the exhaust gas on the road. Take Causeway Bay as an example, there are always people smoking alongside the roads where countless vehicles come and go. In a busy city, it is almost impossible to avoid going to these crowded places outdoors. How about staying indoors? In fact, there is also danger in poorly ventilated workplaces, food premises or at home while using faulty or poorly vented fuel-burning appliances, such as gas water heater and gas stove. Other examples of poorly ventilated areas include car parks and cross harbour tunnels.

To sum up, carbon monoxide is a toxic gas that can cause numerous respiratory illnesses and health impacts as serious as death. In Hong Kong, exhaust gas from large vehicles is the major contributing factor to the accumulation of CO in air. It is of utmost importance for us to educate ourselves and raise awareness about conserving our air quality. Hopefully this article has made you become more alert about the impacts of this invisible yet damaging air component. Take care and stay safe!

Find out more about the CO poisoning situation locally below!

The local situation

In Hong Kong, CO poisoning accounts for dozens of emergency department visits and hospitalisations each year.

According to records of Accident & Emergency Departments (AED) of the Hospital Authority, there were 381 patients recorded as CO poisoning cases, including 43 accidental and 338 intentional cases from January 2012 to December 2016 (Table 1). Of the 43 accidental CO poisoning cases, 53% were female and 56% belonged to the age groups of 31-40 and 51-60 years. None of these accidental cases ended up being fatal.

Table 1: Number of AED attendance in public hospitals related to CO poisoning (2012-2016)

Year Total number of cases Number of cases related to accidental causes Number of cases related to intentional causes
2012 97 2 95
2013 72 5 67
2014 51 11 40
2015 77 71 71
2016 84 19 65
Total 381 43 338