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The secondary pollutants formation in the atmosphere, such as ozone (O3), comes from the reactions between volatile organic compounds (VOCs) and the photochemical oxidants in the presence of oxygen and nitrogen oxides (NOx). The understanding of VOCs reactivity emitted by light duty vehicles is very important to construct reactivity scales regarding ozone formation. In 2003, flex-fuel vehicles were released in the Brazilian market and nowadays, they represent over 50% of the total light duty vehicle fleet in the country. In 2007, new tailpipe emission limits were implemented for Non-Methane Hydrocarbons (NMHC), a group of pollutants included in VOCs. The new NMHC limit became a challenge to homologate some flex-fuel models, when fueled with ethanol. To deal with this issue, other legislation allowed the subtraction of the unburned ethanol emission from the NMHC value.

The Brazilian National Program for Motor Vehicle Pollution Control (PROCONVE) was created in 1986, following USA legislation, including FTP-75 dynamometer driving cycle. This program is going on with success in the reduction of emission limits through the years aiming the improvement of air quality in Brazilian big cities. Since January 2009, PROCONVE phase L-5 establishes emission limits for new light-duty vehicles sold in the country, including: NMHC (Non Methane Hydrocarbons), CO, NOx and Total Aldehyde (Formaldehyde and Acetaldehyde). Next PROCONVE phase, L-6 that will start in 2014, will not include limits for NMOG (Non Methane Organic Gases), which is legislated in USA Tier 2, a relevant emission parameter in terms of ozone production. For the L-6 will be available in the country, a 50 ppm low-sulfur gasoline for vehicle emission homologation, similar to a USEPA standard gasoline.