air and water

2. any species (plant, animal, bird, insect or even bacteria) that reflects the condition of its environment
7. the thinning of Earth's ozone layer in the upper atmosphere
8. a reduction in the pH of the ocean over an extended period of time
10. excessive enrichment of a water body with nutrients, primarily nitrogen and phosphorus
11. ozone forms when pollutants like nitrogen oxides (NOx) and volatile organic compounds (VOCs) react in the presence of sunlight.
12. the gases in the atmosphere that raise the surface temperature of planets such as the Earth
14. A noxious mixture of particulates and gases that is the result of urban air pollution.
15. a meteorological phenomenon where cooler air is trapped near the ground by a layer of warmer air above

1. the presence of harmful substances in the atmosphere that originate from natural sources
3. a natural phenomenon where the Earth's atmosphere traps heat, warming the planet and making it habitable for life
4. the presence in or introduction into the environment of a substance or thing that has harmful or poisonous effects.
5. the increase in the planet's overall average temperature in recent decades
6. The process, in an ecosystem, in which a higher concentration of a substance in an organism is obtained higher up the food chain
9. any other form of precipitation that is unusually acidic
13. Any solid or liquid in a subdivided state, especially one that exhibits special characteristics which are negligible in the bulk material.