California’s cap and trade system will begin operation in 2013. It will be the most ambitious, comprehensive climate change program in the U.S., helping California reduce emissions to 1990 levels by 2020: 6% below 2009 levels and 12% below the peak in 2007.

As our recent analysis shows, if greenhouse gas and air quality regulators work together effectively, cap and trade can bring cleaner air to California and better health to Californians.

California’s Air Resources Board has already taken a step in the right direction, requiring large facilities to conduct industrial audits to assess energy efficiency opportunities that will lead to greenhouse gas and local air pollution emissions reductions.

The data from these audits are slated to be available online by the end of this year. It’s not yet clear what level of detail the data will provide, but more detail is better: It means a larger number of people will know exactly where facilities can make changes that will yield cleaner air.

Detailed, publicly available data from industrial audits will help advocates and the public ensure we’re maximizing public health benefits from our air quality and climate policies by pressuring facilities to undertake energy efficiency improvements wherever possible.

As our analysis shows, whether cap and trade reduces local air pollution depends on which strategies facilities use to reduce greenhouse gas emissions. Energy efficiency is one of the best strategies from a public health perspective, because it reduces both greenhouse gas emissions and local air pollution.

If advocates know where the most cost-effective pollution reductions are, they can push for policy that saves money and benefits public health. And community members can push for facility improvements if they know where they are possible. The health of people near these facilities is directly affected by the measures facilities choose, and this process ought to be as transparent as possible to local residents.

We’ve already seen the power of greater transparency at the national level: When the Environmental Protection Agency released data earlier this year on facility-level greenhouse gas emissions, it drew media and public attention to the biggest emitters, putting pressure on them to improve environmental performance.

Some facility managers may argue publicizing detailed data will give their competitors information they’d prefer not to share. Knowledge of a competitor’s outdated or inefficient production technologies may indeed be advantageous, but that only provides additional incentive for facilities to improve their operations.

Further, facilities may be able to learn best practices from others and replicate low-cost pollution-reducing strategies. Again, this is beneficial to the public, because it means competitive pressure as well as policy will be working to reduce emissions and improve air quality. The regulation protects trade secrets, which facilities will surely define broadly; regulators will need to scrutinize these claims critically.

Transparency can go far in making policy work better. In this case, the information being collected has important implications for multiple policies and stakeholders, making communication between advocates and regulators especially important. Open access to these data could also help build public confidence in both the policy and the regulated facilities.

Putting detailed data in the public sphere has the potential to make possible significant improvements in public health at no extra cost.