I am humbled to be selected for the Urology Care Foundation™ Research Scholar Award, which supports my project studying the impact of wildfire smoke on human sperm under the guidance of my mentor, Thomas Walsh, MD, MS. The support of the Research Scholar Award provides the protected time needed to complete the project, present the work at conferences such as the Annual Meeting of the AUA and the Western Section of the AUA, write manuscripts, and submit grants. Moreover, the Research Scholar Award is allowing me to develop a unique niche as a surgeon-scientist focused on male infertility and environmental health.

I was born and raised in Seattle, Washington, just a few miles from the University of Washington, where I am a newly appointed assistant professor in the Department of Urology. I don’t recall air quality issues affecting my childhood in Seattle, but in recent memory, unhealthy air quality associated with wildfire smoke has become a seasonal event in the Pacific Northwest. The wildfire smoke events that I personally experienced while growing my young family stimulated my interest in how wildfire smoke exposure affects human sperm. In early September 2020, high winds pushed smoke from eastern Washington wildfires into the Puget Sound region. The air smelled of smoke, and ash fell around Seattle while air quality in the Puget Sound region declined to hazardous levels.¹ In multiple regions of Oregon, aggressive wildfires burned nearly a million acres of forest and ultimately threatened Portland suburbs. September 2020 was a notable smoke event, and seasonal wildfire smoke events are now part of life in the Pacific Northwest. Wildfire smoke exposure is emerging as a national and global concern, with a particularly intense year of destructive and deadly wildfires worldwide in 2023. As climate change reduces winter snowpack and produces hotter and drier summers, wildfires are increasing in frequency and intensity.²

It is well established that wildfire smoke exposure is a major threat to human health and that most of the health effects are mediated by fine particulate matter from burning vegetation, synthetics, and other materials.^1-3 Wildfire smoke exposure has been linked to respiratory problems, heart attack, stroke, lung cancer, and cognitive impairment.⁴ A higher risk of testis cancer has been observed among firefighters,⁵ suggesting that the male reproductive tract may be a target of wildfire smoke. However, it is not known how wildfire smoke exposure affects human gametes and reproduction. Infertility affects 1 in 6 individuals worldwide, and a male factor is identified in up to 50% of couples.⁶ In a study using mice, widespread epigenetic changes in sperm were observed after simulated wildfire smoke exposure.⁷ A decrease in total motile sperm count was observed during the September 2020 Pacific Northwest wildfire smoke event in Portland, Oregon, among a small cohort of individuals undergoing intrauterine insemination (IUI), a common fertility treatment in which a purified motile sperm solution is placed into the partner’s uterine cavity at the time of expected ovulation.⁸ This is the first report, to my knowledge, of wildfire smoke exposure impacting human gametes. Couples with infertility undergoing treatment may be especially vulnerable to environmental exposures such as wildfire smoke events.

The overall hypothesis of our study is that wildfire smoke has harmful effects on human sperm. Our project focuses on a period of unhealthy air due to wildfire smoke that occurred in Seattle, Washington, in September 2020 (Figure). First, we are conducting a study of sperm donors who underwent serial sperm donations prior to, during, and in the 3 months after September 2020 in Seattle, given that spermatogenesis occurs over 74 days in humans.⁹ Sperm donor subjects completed questionnaires to estimate their smoke exposure. Using banked samples from these sperm donors, we are performing sperm DNA integrity assessment with the comet assay, a single-cell gel electrophoresis assay that detects double-stranded DNA breaks.¹⁰ This will allow us to evaluate changes in sperm DNA integrity associated with wildfire smoke exposure over time in the same sperm donor subjects. In the second part of our study, we are evaluating sperm quality at the time of IUI procedures performed in the period prior to, during, and after September 2020 in Seattle. We are comparing the total motile sperm count for patients who underwent IUI during or after the wildfire smoke event in September 2020 in Seattle to sperm parameters from the same subject at the time of their diagnostic semen analysis obtained prior to smoke exposure. Understanding whether sperm parameters at the time of IUI are affected by wildfire smoke exposure will be important for counseling patients to mitigate exposures. As wildfire smoke exposure events increase in intensity and frequency, it is critical to understand the impact of wildfire smoke on sperm quality and reproductive outcomes.

In addition to regular interactions with my research mentor, Dr Walsh, the support of the Research Scholar Award is allowing me to participate in several career development opportunities provided by the AUA. I am a mentee in the Urology Scientific Mentoring and Research Training Academy (USMART) program and have regular meetings with a new mentor outside my institution, Dr James Hotaling. I am also participating in the AUA’s Early Career Investigator’s Workshop in Linthicum, Maryland. I am very grateful to the AUA, the Urology Care Foundation™, and the Western Section for supporting my work on wildfire smoke and human sperm. I hope to publish this work in AUA journals such as the The Journal of Urology^®. Ultimately, I expect this will provide preliminary data for a prospective study of wildfire smoke and male fertility. My next step will be to apply for an individual career development award from the National Institutes of Health toward my goal of developing an independent research program in male infertility and environmental health.