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As we plan to accommodate an additional two billion people on the planet over the next 35 years, and with an increasing majority expected to live in urban areas, it is imperative that we learn to resolve tension between residents and nearby industry. It is often low-income and otherwise disenfranchised communities that suffer the impacts of industrial activity, a trend that has given rise to the environmental justice movement. In addition to the negative impacts on residents themselves, industrial-residential conflicts create challenges for regulatory agencies and local government.

One cause of such tension is industrial air pollution and associated odors impacting residents’ health and quality of life. This project addressed the exposure of Globeville, Denver residents to a coal tar odor that is occasionally strong enough to cause burning eyes and throat, headaches, skin irritation, and problems sleeping. Despite numerous requests from residents to the Colorado Department of Public Health and Environment (CDPHE), Denver Environmental Health (DEH), local and state representatives, and the nearby industries, the problem has not been addressed. The coal tar odor is intermittent and unpredictable, frustrating efforts of CDPHE field inspectors attempting to respond to odor complaints. Nearby industries with coal tar- and asphalt-related activities maintain that they are acting within their air quality permits, and CDPHE has supported their claims citing lack of evidence to the contrary. In response, Globeville Civic Association #1 and Groundwork Denver mobilized to address the odor issue by attempting to identify pollutants responsible for the odor and to link these pollutants with offending facilities.

Figure 1. Compounds measured during odor episodes.

Efforts to identify the odor and its potential sources included a door-to-door survey, meteorological correlations, and air quality sampling for a panel of volatile organic compounds (VOCs), sulfur gases, and polycyclic aromatic hydrocarbons (PAHs). Wind speed and direction data collected every one minute in the neighborhood indicate that, when the odor is noticed, the community is directly downwind of a wood preservation facility (Koppers Inc.) and an asphalt roofing facility (Owens Corning). Air samples collected during high intensity odor events thus far have shown concentrations of methylene chloride, hexane, toluene, naphthalene, dibenz(a,h)anthracene, benzo(g,h,i)perylene, and indeno(1,2,3-cd)pyrene each at least two times higher than background concentrations (see Figure 1).

Naphthalene and the other PAHs are known pollutants emitted from the wood treatment processes used by Koppers, and are known to have a coal tar odor. Furthermore, naphthalene was present in a sample collected directly adjacent to the Koppers facility and was not present in any background samples. This data, though limited, suggests the possibility that Koppers is in part responsible for the coal tar odor impacting the Globeville neighborhood.

Odor threshold literature, however, states that naphthalene odor is not detected at concentrations lower than 80 ppb, and the highest concentration sampled thus far is 25 ppb. The odor threshold literature itself highlights another challenge to environmental engineers: there is a complete lack of understanding regarding odor thresholds of mixtures. Given that residents are never exposed to a single pollutant, but always to mixtures, this gap in the literature threatens to relegate the entire body of odor literature to irrelevance. It is perhaps for this reason that odor enforcement in Colorado relies on human interpretation via the imprecise scentometer – a device through which one inhales an ambient sample at a known dilution factor to gauge the strength of an odor.

Given these technical and regulatory challenges, the greatest hope for solving Globeville’s odor issue lays in establishing a “good neighbor policy” between residents and nearby industry. The hope is that specific offending industrial processes can be identified for which there exist cost-effective control technologies. In the process, this work illuminates valuable lessons regarding industry-resident relations, environmental justice, and odor sampling that will inform the coming generation of environmental engineers working in a more crowded world.