The conspicuous haze over China in mid- to late October 2007 not only obscured the view of the land surface. It also contained substances harder to detect but just as troublesome. Odorless, colorless, and toxic, carbon monoxide can be lethal in large amounts. Additionally, it acts as a precursor to smog and ground-level ozone.
From October 16 to 22, 2007, Measurements of Pollution in the Troposphere (MOPITT) measured carbon monoxide over China and Southeast Asia, throughout the air column (between the ground and the top of the atmosphere). In this image, dark red indicates the highest levels of carbon monoxide while pale yellow indicates the smallest. Areas of insufficient data due to clouds appear as light gray (over land) or dark gray (over water). The heaviest concentrations of carbon monoxide appear along the coast, extending from Southeast Asia northward into China, forming a roughly diagonal band in this image. Carbon monoxide also reaches across the water to Japan and beyond, although the concentrations diminish in the southeast.