Press Releases
Feb. 21, 2011

Dangerous oxygen

— Discovery of long-lived reactive forms of oxygen on atmospheric particles —
Presenters
  • Manabu Shiraiwa (Max Planck Institute for Chemistry, the University of Tokyo)
  • Ulrich Pöschl (Max Planck Institute for Chemistry)
  • Markus Ammann (Paul Scherrer Institut)

Abstract

We have made an important step in unveiling the development of toxic and allergy-causing substances in the air: for the first time, we were able to prove the existence of long-lived reactive oxygen intermediates on the surface of aerosol particles. The intermediates are formed by the reaction of ozone with fine particulate matter such as soot, polycyclic aromatic hydrocarbons or pollen proteins. Once formed, the oxygen intermediates can undergo reaction with other air pollutants such as nitrogen oxides leading to oxidized and nitrated compounds that make soot particles more toxic and increases the allergy-inducing effect of pollen.

Researchers from the Max Planck Institute for Chemistry, the University of Tokyo and the Paul Scherer Institute in Switzerland have now shown that the reactive forms of oxygen survive for more than 100 seconds on the surface of aerosol particles, which is long enough to react with other air pollutants. Although it was suspected for years that such intermediates may exist, it was believed that they disappeared in fractions of seconds, and had therefore little impact on the chemical cycles in the atmosphere. The intermediates are also important in many atmospheric and physiological reactions.

The increase of allergies in industrialized countries is linked to these reactions. The more ozone and nitrogen oxides are produced by industrial and traffic emissions, the more frequently organic molecules such as birch pollen proteins are being nitrated and thus elicit responses of human immune system. It has been reported that nitrated proteins can indeed cause more severe allergic reactions. If this hypothesis is confirmed, human health would be endangered by combustion-related emissions even more than previously thought.

The reactive oxygen intermediates may also explain some of the adverse health effects of diesel soot and tobacco smoke particles. The polycyclic aromatic hydrocarbons residing on the surface of these particles readily react with ozone and form reactive oxygen intermediates that persist long enough to be inhaled and interact directly with physiological processes in the human lung and body.

In addition, the oxygen intermediates may have an indirect effect on our climate, because they are likely involved in the formation and growth of fine organic particles from volatile organic compounds emitted from both natural and anthropogenic sources such as vegetation and industrial activities. These particles scatter sunlight and influence the formation of clouds and precipitation, thus affecting the Earth's energy balance and hydrological cycle.

Paper information

Manabu Shiraiwa, Yulia Sosedova, Aurélie Rouvière, Hong Yang, Yingyi Zhang, Jonathan P. D. Abbatt, Markus Ammann, Ulrich PÖschl, The role of long-lived reactive oxygen intermediates in the reaction of ozone with aerosol particles, Nature Chemistry, Published online on 20 February 2011.

Figure 1

Figure 1. The chemical structure of nitrated protein. The NO2 functional group is added to tyrosine amino acid residues. The picture shows nitrated proteins (yellow) and native proteins (white). The nitration not only changes colors from white to yellow, but also increases the allergenicity of proteins.

Figure 2

Figure 2. The chemical structure of nitrated protein. The NO2 functional group is added to tyrosine amino acid residues. The picture shows nitrated proteins (yellow) and native proteins (white). The nitration not only changes colors from white to yellow, but also increases the allergenicity of proteins.