Moss can accumulate airborne contaminants providing insights into air quality.

 Air quality is recognized as a major global health issue by the World Health Organization. Urban areas with high population densities near manufacturing can be particularly vulnerable to contaminants that are the by-products of industrial processes. Detecting point-source pollution often relies on disclosures or citizen complaints and can be ineffective. Expensive air quality monitoring equipment often provides coarse scale regional air quality that fails to locate hotspots where contaminant levels reach unsafe levels. New techniques to detect air pollution are being implemented that provide regulators with valuable information that can be used to protect public health in urban areas at lower costs.

Poor air quality and smog in Tacoma pose a risk to human health

Airborn contaminants are a major health concern that have both chronic and acute effects on human populations (Kampa & Costanas, 2007). These effects can range from respiratory irritation to chronic diseases cancer and premature mortality. Perspectives on environmental justice have further informed the unequal distribution of industrial pollution in poor and minority communities (Goldman, 1994) highlighting the need for locating hotspots of pollution and improving access to clean air.
Air quality is traditionally monitored by sophisticated instruments that inform coarse resolution regional air pollution, such as Washington’s Air Monitoring Network operated by the Department of Ecology. 

WA Dept. of Ecology’s Air Quality Network provides regional scale information. WA’s Air Quality Network

The instruments in this network are expensive and require regular maintenance, which limits the number of monitors that can feasibly be deployed in urban areas (Shang, 2017). As a Physical Science Technician at Big Bend National Park in west Texas, I operated an air quality station. It required weekly calibrations and checks that took the better part of a day. I replaced filters, collected water samples, all to be shipped to distant laboratories for analysis. The facility was the size of a shipping container with additional towers and instruments scattered throughout the area. As a regional station, it gave a coarse estimate of different airborne contaminants, but could not detect finer scale source pollution. For example, regional increases in particulate matter caused by winds pushing in smog from industry near Houston could be detected, but a smaller plume of contaminants from a closer city would likely go undetected. Big Bend is remote and rural, but urban areas with high population density and plenty of sources of industrial pollution could benefit from higher resolution data sources. 

Traditional air quality monitoring sensors provide coarse regional information about pollutant levels. They can be expensive to operate and generally do not identify neighborhood scale risks.

Lichens and mosses have been used internationally as biomonitors of air quality. Atmospheric pollution settles on moss and accumulate over time, helping scientists to identify hotspots for contamination. These techniques can be more cost effective because they do not require continuous monitoring by expensive equipment. Some technique involves the placement of moss bags throughout a city. This allows for a more standardized sample than collection of wild moss. In Shanghai, China this technique found higher concentrations of lead and other contaminants in the industry district (Cao et al 2006)

Moss bags are an effective and inexpensive way to detect contaminants. (source: http://www.envpl.ipb.ac.rs/bio2.htm)

Alternatively, where naturally occurring moss is abundant, researchers can collect samples from the environment. Laboratory analysis involves dryings samples and analyzing the elemental contaminants that have settled on the moss (Gatziolis et al., 2016).

In Portland Oregon, a recent study led by the US Forest Service collected hundreds of epiphytic samples of Orthotrichum moss from across the Portland region (Gatziolis et al., 2016). Results can produce relatively high resolutions of pollution hot spots that may pose a threat to human health. The report found that unacceptable levels of several contaminants were in dense residential areas and near schools. Each moss sample costs about $150 for labor and lab analysis while a permanent air toxics monitor costs $40,000 annually to operate.

Map of lead pollution hot spots in Portland detected using moss samples from Gatziolis and colleagues (2016)

One notable disadvantage of the bioindicator method is that it provides relative values, not actual concentrations or specific time periods that inform health concerns (Gatziolis et al., 2016). Because of this, further investigation may be required to accurately identify public health threats. One example of how data can inform health authorities is the modeled distribution of arsenic.

Models take the moss data points and produce higher resolution maps of hotspots from OregonLive.com

Researchers suggests more investigation of the relationship between values found in moss and the actual atmospheric levels to further refine bioindicator methods. For example, each element may accumulate differently in moss, likely providing a window of inference ranging from a several months to a few years . Refinement for particular moss species should also be a high priority for future studies using bioindicators because each element may bond differently with moss. Climatic effects such as precipitation, humidity and temperature may also effect the strength of the relationship to atmospheric levels.

This type of moss biomonitoring has not been conducted in the Olympia area. While we may not be a center for manufacturing, there are some point sources of toxic chemicals located within 5 miles of The Evergreen State College that are still awaiting clean up. 

Toxic sites identified by the Department of Ecology within 5 miles of The Evergreen State College

It may provide insights into  health risks and pollution hotspots  to use biomonitoring techniques near identified clean-up sites or other industrial areas.  For example, a biomonitoring program detected cadmium pollution from a stained glass factory in Portland, OR as described by this OPB article.

References

Cao, T., Wang, M., An, L., Yu, Y., Lou, Y., Guo, S., … & Zhu, Z. (2009). Air quality for metals and sulfur in Shanghai, China, determined with moss bags. Environmental Pollution, 157(4), 1270-1278.

Gatziolis, D., Jovan, S., Donovan, G., Amacher, M., & Monleon, V. (2016). Elemental atmospheric pollution assessment via moss-based measurements in Portland, Oregon. United States Department of Agriculture, Forest Service, Pacific Northwest Research Station.

Goldman, B., & Fitton, L. (1994). Toxic wastes and race revisited. Washington, DC: Center for Policy Alternatives.

Kampa, M., & Castanas, E. (2008). Human health effects of air pollution. Environmental pollution, 151(2), 362-367.

Shang, M. G. (2017). Low Cost Air Quality Monitoring. Thesis. Portland State University

Susan, W. W., Jovan, S., & Amacher, M. C. (2017). Lichen elements as pollution indicators: evaluation of methods for large monitoring programmes. The Lichenologist, 49(4), 415-424.

WHO, 2016. World Health Organization. “Ambient (outdoor) air quality and health” Accessed: http://www.who.int/mediacentre/factsheets/fs313/en/