California Code, Health and Safety Code - HSC § 43700

(a) Significant reductions in diesel emissions from existing vehicles can be achieved by the adoption of stricter diesel fuel specifications on sulfur, aromatics, and other fuel properties.

(b) The state board, in consultation with the State Department of Health Services, is evaluating the potential carcinogenic effects of specific constituents of diesel exhaust. Diesel exhaust is known to include, as constituents, many substances known or suspected to be toxic air contaminants.

(c) The Environmental Protection Agency has agreed to study the health effects of various fuels, including diesel, to determine the relative impacts on public health and the environment.

(d) Notwithstanding the ongoing study and review, reduction of emissions from diesel powered vehicles, to the maximum extent feasible, is in the best interests of air quality and public health.