The Inter-governmental Panel on Climate Change (ipcc) estimates that the range of stabilised atmospheric carbon-dioxide concentration by 2050 will be between 450 parts per million (ppm) and 550 ppm. A paper published in the journal Current Science (Vol 90, No 12) argues that these concentration levels have not been correlated to health impacts. According to the paper, 426 ppm is the permissible exposure over a lifetime.

The author says that increasing levels of carbon dioxide, apart from affecting climate, will have serious toxic effects on humans and other mammals.

Higher carbon dioxide concentration affects health by reducing blood ph causing difficulty in breathing, rapid pulse rate, headache, hearing loss, sweating and fatigue. Some studies have also shown possibilities of embryonic or foetal abnormalities due to increase in atmospheric carbon dioxide.

A study on health effects of high indoor carbon-dioxide concentrations has established that at 600 ppm, occupants felt stuffy, and above this level, symptoms of poisoning started to show. At 1,000 ppm, nearly all the occupants were affected.

All these effects were observed with only a transient exposure and not over a lifetime. On an average, carbon-dioxide levels in offices reach 800-1,200 ppm and up to 2,000 ppm in overcrowded conference rooms.

At present, carbon dioxide concentration in the atmosphere is about 380 ppm.

When it reaches 600 ppm, the earth will have a permanent outdoor atmosphere exactly like that of a stuffy room, which life may not adapt to.

— CSE/Down to Earth Feature Service