émission naturelle de CO

OBS: (...) monoxyde de carbone (CO) (...).

CONT: These LDV-related pollutants are also emitted from natural sources. For example, in Canada, natural CO emissions are estimated to be 260 000 tonnes per year, and natural emissions of NOx have been variously estimated to be one million and 2.7 million tonnes per year.
OBS: ... carbon monoxide (CO) ....
OBS: Carbon monoxide emissions ....