Final answer:
The correct answer is A, as asbestos, radon, and urea formaldehyde are all classified as environmental hazards due to their health risks and potential to harm the environment.
Step-by-step explanation:
The correct answer is option A: classified as environmental hazards. Asbestos, radon, and urea formaldehyde are well-known for their adverse health effects and are considered as substances that may pose a threat to human health and the environment.
Asbestos was historically used in construction and other industries for its durability and resistance to heat, but it is now recognized as a major health hazard that can cause lung diseases, including cancer.
Radon is an odorless, colorless gas that emanates from the natural decay of uranium in soils and can accumulate in homes, increasing the risk of lung cancer, particularly among non-smokers. Urea formaldehyde is found in many household products and building materials, releasing formaldehyde gas that can cause various health problems. All these substances are regulated to minimize their impact on indoor air quality and overall public health.