PHE 540 Module 10 Final Project Example

Breathing Next Door to a Sterilizer: A Human Health Risk Assessment of Ethylene Oxide in a Tennessee Valley City

[Student Name]

Southern New Hampshire University

PHE 540: Principles of Environmental Health

Final Project

[Instructor Name]

[Date]

The organization, setting and figures below are a composite written as a model document. No real employer, client, colleague or patient is described.

Breathing Next Door to a Sterilizer: A Human Health Risk Assessment of Ethylene Oxide in a Tennessee Valley City

Executive Summary

A medical device sterilizer releases ethylene oxide, a known human carcinogen, about 400 meters from an apartment complex and an elementary school. A year of air sampling found the plant adding about 0.5 micrograms per cubic meter at the apartments, falling to 0.05 at 1,500 meters. Using the EPA's cancer potency values, a child living in the apartments from birth to age eleven carries an estimated added lifetime cancer risk of about 1 in 1,000; an adult living there ten years about 1 in 7,000. Both exceed the range regulators generally treat as acceptable. The assessment recommends early installation of fugitive emission controls, fence-line monitoring, plain-language updates for residents and a zoning review for future housing.

Scope and Approach

The assessment follows the four steps the National Research Council (1983) set out and keeps the scientific estimate separate from management recommendations. It covers inhalation of ethylene oxide from the plant by residents, students and staff within two kilometers, with cancer as the endpoint. Plant workers and other sources are outside its scope; background is measured and reported but not attributed to the plant.

Hazard and Dose-Response in Brief

Ethylene oxide causes cancer in people by damaging DNA. Worker studies link it to lymphoid cancers and, with an exposure-response trend, to breast cancer (Steenland et al., 2003). The EPA's 2016 evaluation classified it as carcinogenic to humans and assigned adult exposure a cancer slope, the inhalation unit risk, of 0.003 for each microgram per cubic meter breathed over a lifetime, with age-dependent adjustments because of its mutagenic action: exposure before age two is weighted tenfold and from two to sixteen threefold (U.S. Environmental Protection Agency, 2016). A linear, no-threshold model is assumed.

Exposure Summary

A year of 24-hour samples across five locations gave annual means of 0.22 micrograms per cubic meter at the upwind background site, 0.71 at the apartments, 0.58 at the school, 0.34 at 1,000 meters and 0.27 at 1,500 meters. Subtracting background and weighting by time spent at each location gave the plant increments used below. Calm nights at the apartments produced readings two to three times the annual mean.

Risk Characterization

Added lifetime cancer risk equals the long-term average concentration multiplied by the unit risk, scaled by the fraction of a 70-year lifetime exposed and, for children, by the age adjustments. For the child, the adjusted factor is 3 × 10⁻³ multiplied by (10 × 2 + 3 × 9) divided by 70, or about 2.0 × 10⁻³ per microgram per cubic meter. Table 1 shows each group.

Table 1. Estimated added lifetime cancer risk from the plant

Note. Risks are added to background and to all other causes of cancer.

Comparison With Benchmarks

Federal air toxics programs generally aim for added lifetime risks no higher than about one in a million for most people and treat one in ten thousand as an upper limit of acceptability. The child estimate is roughly ten times that upper limit, the adult resident estimate exceeds it and the homeowner estimate sits at it. Only school staff fall within the range. By comparison, Olaguer et al. (2020) estimated a peak risk near one in one hundred for neighborhoods beside a larger Michigan facility, so the local plant appears less severe but still clearly in need of control.

Uncertainty and Variability

Several uncertainties affect these estimates. The unit risk is extrapolated from workers exposed at far higher concentrations; if low-dose risk is smaller than the linear model assumes, true risks would be lower. Using the lowest and highest seasonal means, the child estimate ranges from about 6 in 10,000 to 13 in 10,000. Indoor concentrations were assumed equal to outdoor ones. Twenty-four-hour samples smooth over night peaks. And durations are assumptions; a child who moves away at age five would have lower risk, while one who stays into adulthood would have more. Variability matters as much as uncertainty: risks fall sharply with distance, so the apartments carry far more than the wider city.

Background raises a further difficulty. By the same unit risk, the measured background of 0.22 implies an added lifetime risk around one in a thousand for everyone in the region. That figure is uncertain and debated, but it does not make the plant's contribution acceptable, because the plant's share can be controlled and falls on a small, identifiable group.

Risk Management Recommendations

Management decisions belong to the plant, the state agency and the city, informed by this assessment. Four steps are recommended. First, the state should require the plant to install fugitive emission controls on aeration rooms and the warehouse within twelve months, ahead of the federal schedule, and the plant has signaled willingness. Second, two fence-line monitors should report weekly, with results posted publicly. Third, the city should require that any proposed housing near a licensed source of toxic air pollution be reviewed for emissions before approval. Fourth, the health department should repeat neighborhood sampling one year after controls are installed to confirm that risks have fallen. Because the nearest residents are disproportionately renters and lower-income households, these steps also address the environmental injustice that Mohai et al. (2009) describe.

Risk Communication

The communication plan aims to make residents partners rather than audiences, the final stage Fischhoff (1995) described. Results will be presented first to the tenant association with a simple picture of risk, an explanation of uncertainty and a focus on the actions above, then delivered door to door in English and Spanish. Updates will follow every quarter, and residents on the advisory group will help choose new monitoring sites.

Conclusion

The sterilizer adds a measurable and avoidable cancer risk to the people living closest to it, highest for young children in the apartments. The risk is not an emergency, but it is well above what regulators aim for and falls on a neighborhood with little power to change it alone. Controlling fugitive emissions, verifying the results and keeping residents informed and involved would bring the risk down and rebuild trust.

References

Fischhoff, B. (1995). Risk perception and communication unplugged: Twenty years of process. Risk Analysis, 15(2), 137-145. https://doi.org/10.1111/j.1539-6924.1995.tb00308.x

Mohai, P., Pellow, D., & Roberts, J. T. (2009). Environmental justice. Annual Review of Environment and Resources, 34, 405-430. https://doi.org/10.1146/annurev-environ-082508-094348

National Research Council. (1983). Risk assessment in the federal government: Managing the process. National Academy Press. https://doi.org/10.17226/366

Olaguer, E. P., Robinson, A., Kilmer, S., Haywood, J., & Lehner, D. (2020). Ethylene oxide exposure attribution and emissions quantification based on ambient air measurements near a sterilization facility. International Journal of Environmental Research and Public Health, 17(1), Article 42. https://doi.org/10.3390/ijerph17010042

Steenland, K., Whelan, E., Deddens, J., Stayner, L., & Ward, E. (2003). Ethylene oxide and breast cancer incidence in a cohort study of 7576 women (United States). Cancer Causes & Control, 14(6), 531-539. https://doi.org/10.1023/A:1024891529592

U.S. Environmental Protection Agency. (2016). Evaluation of the inhalation carcinogenicity of ethylene oxide (CASRN 75-21-8) in support of summary information on the Integrated Risk Information System (IRIS) (EPA/635/R-16/350Fa). U.S. Environmental Protection Agency.