Rising CO2 levels may appear in human blood, posing toxicity risk in 50 years

A new study suggests that rising atmospheric carbon dioxide levels may already be detectable in human blood, and researchers warn that within 50 years, outdoor air could become “potentially toxic” to humans. The research, published in the journal *Sustainability*, indicates that CO2 concentrations in the air are approaching levels that could impair cognitive function and pose health risks to the general population.

The study affects everyone who breathes outdoor air, but particularly vulnerable groups include children, the elderly, and people with respiratory conditions. As CO2 levels rise, the gas accumulates in enclosed spaces and can enter the bloodstream, potentially leading to reduced decision-making abilities, headaches, and drowsiness. The researchers emphasize that this is not just an indoor problem—outdoor CO2 concentrations are also climbing.

This matters because current climate models project that by 2070, atmospheric CO2 could reach 550 parts per million (ppm) or higher, a level that some studies have linked to cognitive decline. The study’s lead author, Dr. Mark Jacobson of Stanford University, notes that at 1,000 ppm, indoor air quality standards are already considered poor, and outdoor levels are on track to exceed that threshold in many urban areas within decades.

The source provides specific numbers: today’s global average CO2 is about 420 ppm, up from 280 ppm before the Industrial Revolution. The study warns that if emissions continue unchecked, outdoor CO2 could hit 550 ppm by 2070, and in poorly ventilated cities, levels could spike even higher. The research builds on earlier work showing that CO2 at 1,000 ppm impairs human cognitive performance by 15-50%.

Background: The study is part of a growing body of research on the direct physiological effects of CO2, beyond its role in climate change. Previous studies have focused on indoor environments, but this paper extends the concern to outdoor air. The authors note that CO2 dissolves in blood, forming carbonic acid, which can alter blood pH and affect oxygen delivery.

The likely next steps, according to the source, include urgent calls for stricter emissions reductions and more research on chronic low-level CO2 exposure. The study suggests that governments may need to consider CO2 as a direct pollutant, not just a greenhouse gas, and update air quality guidelines accordingly. Without action, the researchers warn, a “potentially toxic atmosphere” could become a reality within half a century.