I am a developer in the SF Bay Area. I am interested in acquiring a site in Oakland for a mixed use project, but it’s near the freeway and I heard that the Air District has just banned housing near freeways. Is this true?

Not exactly. I believe what you are referring to is guidance that the Bay Area Air Quality Management District (BAAQMD) promulgated recently on how to evaluate health impacts of air pollution from nearby sources such as freeways and refineries on potential new residential developments. The first thing to keep in mind is that what BAAQMD published is not a regulation or a formal rule, but rather guidance for use by your project’s permitting authority (likely the City Planning Department) in their environmental review of your project, to help them determine if air quality impacts warrant additional analysis under CEQA, the California Environmental Quality Act. So you’ll want to check with the city to see how they’re incorporating the new guidance into their CEQA process.

On a larger scale, however, BAAQMD’s new guidelines – which include quantitative thresholds indicating acceptable exposure levels for fine particulate matter (typically referred to as PM_2.5) – have added new fuel to a continuing public policy debate over regulating land use to control the health impacts of localized air pollution. In recent years, a growing body of research has shown that exposure to fine particulate matter (PM_2.5) may cause serious detrimental health effects, including increased asthma risk, pulmonary failure, and bronchitis. Studies have also shown a connection between these health effects and proximity to heavily-trafficked roads; the vast majority of PM in major cities (80% by some estimates) comes from motor vehicle emissions, especially diesel. However, the science also shows a number of challenges with translating this connection to broadly designed regulation.

For one thing, PM is highly variable and can have very different effects depending on its composition. Currently, not much is known about the effects of different types of PM because it is difficult to separate out different components for study. What is clear is that some elements that make up PM are more toxic than others, but little information is available as to which elements should be avoided. Many air quality experts have cautioned against legislating on PM at this time, as there is not enough information on what types and sources of PM are actually harmful to human health.

There are also significant challenges in designing a scientifically defensible method for quantifying and individual’s actual exposure to PM.  Studies have shown that PM exposure can vary greatly depending on a number of factors whose variability make them incredibly difficult to accurately model, including wind patterns, micro-climates, vehicle speed, topography, landscaping, and particle size.

Finally, policy makers must keep in mind that local land use policy can have broader impacts on the local and regional level. Especially given that local PM exposure is typically 1-2 orders of magnitude lower than the ambient air pollution levels urban dwellers are already exposed to, it is important to weigh the real public health benefits of such a policy against the potential for such a policy to drive good development out of urban areas and into suburban and greenfield sites. Not only could such a divestment from our urban communities have dire consequences on the quality of life for existing residents, but driving development to the suburban fringes would actually be counterproductive to the policy’s intent, leading to increased greenhouse gas and diesel emissions and putting the goal of protecting public health today at odds with protecting the environment and public health of tomorrow.

It is important to continue the public debate on the costs and benefits of controlling pollution exposure through land use regulation. However, until the scientific community can reach a consensus on how to reliably and accurately assess the real health effects of local PM exposure, it is premature to impose proscriptive land use restriction. In the meantime, the current guidance by the California Air Resources Board that any new residential project within 500 feet of a major freeway should evaluate air quality impacts is a reasonable approach that allows for site-specific analysis and minimizes unintended consequences.