Performance of essential functions may require exposure to adverse environmental conditions, such as dirt, dust, pollen, odors, wetness, humidity, fumes, smoke, temperature and noise extremes, hazardous materials, fire, unsafe structures, heights, confined spaces, traffic hazards, bright and dim lights, toxic agents, animal and wildlife attacks, animal and human bites, explosives, or rude and irate customers. Tasks require the regular and sustained performance of moderately physically demanding work, typically involving some combination of climbing and balancing, stooping, kneeling, crouching, and crawling, and that may involve the lifting, carrying, pushing, and/or pulling of moderately heavy objects and materials (20-50 pounds).