Project Summary/Abstract Wildfire activity is increasing resulting in greater numbers of firefighters conducting suppression and prescribed fire activities each year to protect lives and property. In conducting these activities, individuals are exposed to occupational factors that increase the risk of acute and chronic illness, including prolonged and elevated exposure to smoke particulate. Fine smoke particulate is known to penetrate the lung and has recently been associated with impacts outside the lung including in the reproductive system. In fact, our lab has demonstrated that laboratory generated wildfire smoke exposure at occupationally relevant levels alters sperm epigenetic patterns in a mouse model. The National Fire Service Research Agenda Report recently highlighted the potential for reproductive risk and stated that infertility issues that result from being a firefighter should be a priority research objective. In response, we have designed three aims to determine the extent to which wildland firefighter activities, particularly wildfire smoke inhalation, impacts fertility among male wildland firefighters. For Aim 1, among 100 wildland firefighters, we will assess cross-season paired samples for concentrations of motile sperm as a marker of fertility and in Aim 2 we will quantify epigenetic modifications in a subset of 50 wildland firefighters as a predictor of quality and offspring health. The outcome of Aims 1 and 2 will be the first characterization of adverse sperm parameters and molecular changes that occur in wildland firefighters following occupational exposure to smoke, which will inform early detection and intervention strategies for occupation-related infertility issues. For Aim 3, we will combine the findings from our study with other current literature to craft messaging material informing firefighter personnel about the potential adverse exposure impacts, as well as precautionary measures which may protect their reproductive health. We will seek feedback via wildland firefighter focus groups (n=20) on how to craft the message as well as what they view as trusted channels for dissemination. The outcome to Aim 3 will be a strategic communication plan that can be adopted and modified by the fire service to enhance the reproductive health and wellbeing of male wildland firefighters.