Carbon dioxide as a pollutant: the risks on human health and the stability of the biosphere

Abstract

The consequences of the human-caused increase in carbon dioxide concentration in the atmosphere are normally discussed mainly in terms of its radiative forcing effect and the consequent global warming and climate change. However, CO₂ is a chemically active molecule in aqueous environments, and it has multiple effects on the biosphere. Increasing CO₂ concentrations in the atmosphere increase the acidity of seawater and harm marine organisms. High CO₂ concentrations can make the photosynthetic reaction faster in some plants but also negatively affect the metabolism of aerobic metazoans, with harmful effects on human health. These effects are already important for people living in closed spaces and can only become stronger with the projected future increases in CO₂ atmospheric concentration. The present paper is a critical review of a field that is important for the future of humankind. We find that the chemical and biochemical pollution associated with CO₂ is a serious problem that may turn out to be no less important than that of radiative forcing in terms of damage to human health and to the whole biosphere. These results also indicate that geoengineering techniques based on Solar Radiation Management (SRM) alone cannot be sufficient to counter the ecosystem disruption caused by anthropogenic CO₂ emissions.