Environmental Engineering is the application of science and engineering principles to protect or improve the environment (air, water, and/or land resources), to provide healthy water, air, and land for human habitation and for other organisms, and to remediate polluted sites. Environmental engineering essentially began in the late 19th Century with consideration of the need for healthy drinking water, and for management and disposal of liquid and solid wastes. Abatement of air and land contamination became the new challenges in the 20th Century for the environmental engineer, followed by concern for toxic and hazardous-waste concerns. Environmental engineers are instrumental in the protection of wildlife habitats, preservation of species through engineered works, and in the overall well-being of ecosystems that are increasingly by human activity. The principal environmental engineering specialties include: air-quality control, water supply, wastewater treatment and disposal, storm water management, solid waste and hazardous waste management. Other specialties, among others, include industrial hygiene, noise control, oceanography, risk assessment and radiology.