Alumni Feature: Protecting Worker Health Through Leadership in Industrial Hygiene and Occupational Safety

For Gregory Day, pursuing a career in industrial hygiene was not part of the original plan — but it ultimately became the professional path that shaped the course of his life and career.

After earning both a Master of Science in Industrial Hygiene in 1996 and a PhD in 2002 from the OU Hudson College of Public Health, Day built a distinguished career dedicated to protecting worker health and safety through environmental and occupational health leadership.

Prior to retiring from federal service in 2025, Day served as an Environmental and Occupational Safety and Health (EOSH) Officer for the Federal Aviation Administration at the Civil Aerospace Medical Institute on the Mike Monroney Aeronautical Center in Oklahoma City.

Before entering the field, Day worked in a successful family-owned jewelry business and held a bachelor’s degree in business administration. But at age 32, encouraged by his stepfather — a hydrologist who recognized his attention to detail — Day decided to pursue an entirely new direction.

“With only a bachelor’s degree in business administration, I took several undergraduate courses in chemistry and mathematics before enrolling in the Industrial Hygiene program,” he said. “I took those prerequisite courses while working full time.”

The transition was challenging, but it quickly became clear he had found the right fit.

“My first two graduate courses were in indoor air quality management and biostatistics, and I quickly learned that I had found my calling.”

As a student in the Industrial Hygiene program, Day discovered a passion for research and analytical problem-solving that would shape the rest of his professional journey.

One of the most influential experiences during his time at HCOPH was working alongside his mentor, Nurtan Esmen, on a Monte Carlo simulation project that became the foundation of his master’s thesis, titled “Sample Size-Based Indication of Normality in Log-Normally Distributed Populations.”

“That work served as the catalyst for my decision to pursue a PhD, a decision that has positively influenced nearly every aspect of my professional career.”

Throughout his career with the Civil Aerospace Medical Institute, Day helped oversee environmental and occupational safety and health programs focused on respiratory protection, hearing conservation and exposure assessment.

He also worked closely with licensed healthcare professionals to interpret industrial hygiene assessments and support medical surveillance efforts that helped safeguard employee health.

For students considering the Industrial Hygiene program, Day emphasizes the importance of commitment, discipline and attention to detail.

“I would tell anyone enrolling in this Industrial Hygiene program that it will require focused attention to detail and commitment to learning a great deal of information in a relatively short period of time,” he said. “But such attention and commitment will reap great rewards in terms of opportunities.”

Through decades of service in occupational health and safety, Day’s career reflects the impact HCOPH graduates continue to make across industries and public service — applying science, leadership and technical expertise to protect the health and well-being of workers and communities alike.