Benzene Emissions in Philadelphia Pose Cancer Risk

     I usually try to read the Philadelphia Inquirer every few weeks or so, just to keep tabs on what's happening back home. When I opened the website tonight I noticed an article entitled 'Greenspace: Proximity to Industrial Plants' Benzene Linked to Cancer'. From the title, it sounded like this article would be a perfect example of a negative externality of production, as large factories and refineries in the southern section of the city had been reported to have been emitting a toxic chemical known as benzene, that health experts have labled a carcinogen. This would fit the paradigm of the negative production externality, as the negative effects of the benzene on surrounding residents raises social marginal costs in the market for the refineries' output above allocatively efficient levels. This cost was being imposed on South Philly residents who were not parties to the exchange in which benzene was produced.
      However, after reading the article, unlike the title misleadingly suggests, the main culprit in benzine emissions is not the refineries, but is instead city traffic, which accounts for triple the amount of benzine emissions in the city. So, while there is definitely a negative production externality at play here, the bulk of the benzine emissions is actually a negative externality of consumption. City drivers are engaging in an activity that, like smoking, imposes an externality on the rest of the city's residents. The result is that the social marginal cost is higher than the private marginal cost to the individual drivers (gas, insurance, car payments) and the quantity of driving 'consumed' is higher than what an economist would consider allocatively efficient.