Oregon wildfires led to unprecedented hazardous air quality in the Pacific Northwest for 10 days in September 2020, blanketing the Portland Metropolitan area in toxic smoke. This study seeks to analyze the post-wash total motile sperm count (TMC) at the time of intrauterine inseminations (IUI) directly following the 2020 Pacific Northwest Wildfire Crisis.

      Materials and Methods

      In this retrospective cohort study, sperm parameter data was collected from IUI performed at a single academic center in Portland, OR from July 2018 to December 2020. All samples were processed by 90% gradient centrifugation for 20 minutes, followed by centrifugation in sperm washing media for 7 minutes and resuspension of the sperm pellet to 0.5 mL for insemination. Samples were compared between those collected prior to and after the onset of hazardous air quality (July 1, 2018-September 9, 2020 vs September 10-December 31, 2020) using Wilcoxon rank-sum tests. We excluded cycles using frozen sperm. Samples were excluded if they did not have a recorded prewash or postwash TMC. The primary outcome was postwash TMC. Secondary outcome was median difference between prewash and postwash TMC. A second analysis consisting only of paired samples collected from subjects with a sample both before and after the onset of hazardous air quality was performed comparing medians using Wilcoxon signed-rank tests.


      Of the 998 fresh collection samples processed in our laboratory, 992 samples from 466 unique individuals met our inclusion criteria, 810 before the onset of hazardous air quality and 182 after. Median postwash TMC was greater prior to the onset of hazardous air quality compared to after the exposure (26.45 mil IQR: 9.6-50.2 mil vs 16.2 mil IQR: 6.4-36.2 mil, p<0.01). Difference between prewash and postwash TMC was significantly less prior to onset of hazardous air quality (68.8 mil IQR: 31.14-132.6 mil vs 88.5 mil IQR: 36.13-163.58 mil, p=0.01). In the paired sample analysis, 63 samples before exposure and 63 samples after exposure, accounting for 39 subjects, met inclusion criteria. In this cohort, the median postwash TMC was greater prior to the onset of hazardous air quality than after (29.84 mil IQR: 10.0-46.2 mil vs 19.62 mil IQR: 10.63-43.12 mil, p=0.03).


      Semen quality was significantly poorer in the three months following the sudden onset of hazardous air quality.

      Impact Statement

      This study highlights the impact of a major toxic air quality pollution event on one of many factors impacting fertility. The increase in number and severity of wildfires in the Pacific Northwest may have serious fertility consequences for subjects living in the region. Larger, long-term studies are needed to fully assess the impact of acute events such as these.