California grossly miscalculated pollution levels in a scientific analysis used to toughen the state’s clean-air standards, and scientists have spent the past several months revising data and planning a significant weakening of the landmark regulation, The Chronicle has found.
The pollution estimate in question was too high – by 340 percent, according to the California Air Resources Board, the state agency charged with researching and adopting air quality standards. The estimate was a key part in the creation of a regulation adopted by the Air Resources Board in 2007, a rule that forces businesses to cut diesel emissions by replacing or making costly upgrades to heavy-duty, diesel-fueled off-road vehicles used in construction and other industries.
The staff of the powerful and widely respected Air Resources Board said the overestimate is largely due to the board calculating emissions before the economy slumped, which halted the use of many of the 150,000 diesel-exhaust-spewing vehicles in California. Independent researchers, however, found huge overestimates in the air board’s work on diesel emissions and attributed the flawed work to a faulty method of calculation – not the economic downturn.
The overestimate, which comes after another bad calculation by the air board on diesel-related deaths that made headlines in 2009, prompted the board to suspend the regulation this year while officials decided whether to weaken the rule.
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