Pulmonary Implications of Lunar Mineral Dust

For extended lunar missions it is critical to understand whether lunar dust is toxic. Terrestrial mineral dusts produce a variety of lung diseases, some of which can occur rapidly. However, the mineralogy of lunar materials differ substantially from what occurs on Earth, so that it is essential to determine whether lunar dusts induce equivalent disease processes. Recent analyses of materials brought back by Apollo have led to the development of a simulant that closely mimics lunar dust. Thus, we now have a powerful research tool that can be used to investigate the biological consequences and mechanisms of disease induction from inhalation exposures. The surface of the lung is covered by a unique fluid layer which inhaled particles contact first and in which many important biological processes occur. Investigations into the interactions between the lunar dust simulant and the lung surface, especially with regard to the potential to induce free radicals and oxidative stress are needed. Chemical model systems can be employed first to define the chemistry, followed by studies using cell cultures so that experimental conditions can be tightly controlled and so that analyses can be accomplished that are not practical within the lung. Studies with experimental laboratory rodents to determine health outcomes in terms of oxidative stress, whether the simulant produces lung inflammation and lung cell injury, and whether simulant exposures produce only acute or more chronic pathology are than practical and necessary. We view these studies as essential because NASA's draft standard for human habitability and environmental health (NASA-STD-3001) requires that “The vehicle/habitat shall control atmospheric pressure; humidity; temperature; ventilation flow rate; airborne particulates; and partial pressure of O2, CO2; and trace constituents within ranges necessary to maintain human health and safety,” but the acceptable ranges of airborne particulate exposures to lunar dusts remain unknown.