With the legal decision in the United States to define CO2 as a pollutant (see), the important question on how to include this climate forcing in the assessment of emssion controls with respect to the traditional primarily health related pollutants need to be considered. For example, should the climate forcing of CO2, which is claimed will result in major changes in the environment, be a more important consideration than the health effects of pollutants such as produced by fuels that are intended to reduce the emission of CO2.
Biofuels have received considerable attention as at least a partial replacement for fossil fuels. However, there are already issues raised by its use [e.g. see (and thanks to Laure M Montandon for alerting me to this article). A major concern are the possible carcinogens and other toxic gases and particles that would be part of the emissions from vehicles or other combustion sources that use this fuel.
There is a summary available entitled “Biodiesel Emissions Compared to Other Fuels
Fuel Types” which provides some insight into this issue. The values in the table presented in this summary are the difference with respect to diesel, whose emissions are a well known health hazard as identified by the American Lung Association, where they write,
“Diesel exhaust is a mixture containing over 450 different components, including vapors and fine particles. Over 40 chemicals in diesel exhaust are considered toxic air contaminants by the State of California. Exposure to this mixture may result in cancer, exacerbation of asthma, and other health problems.
For the same load and engine conditions, diesel engines spew out 100 times more sooty particles than gasoline engines. As a result, diesel engines account for an estimated 26 percent of the total hazardous particulate pollution (PM10) from fuel combustion sources in our air, and 66 percent of the particulate pollution from on-road sources. Diesel engines also produce nearly 20 percent of the total nitrogen oxides (NOx) in outdoor air and 26 percent of the total NOx from on-road sources. Nitrogen oxides are a major contributor to ozone production and smog….
Diesel exhaust has been linked in numerous scientific studies to cancer, the exacerbation of asthma and other respiratory diseases. A draft report released by the US EPA in February 1998 indicated that exposure to even low levels of diesel exhaust is likely to pose a risk of lung cancer and respiratory impairment. And in August 1998, the State of California decided that there was enough evidence to list the particulate matter in diesel exhaust as a toxic air contaminant – a probable carcinogen requiring action to reduce public exposure and risk.”
While biofuels including biodiesel may improve on traditional diesel, health concerns regarding its use will exist. In any regulation on CO2, if it results in increased emssions of gases and aerosols with health issues, then the climate concerns of human inputs of CO2 will have trumped the health effects of the replacement fuels.