Identifying Water Pollutants

Water pollution occurs when harmful substances contaminate water bodies, making them toxic to living organisms and unsuitable for human use. Many different substances can act as water pollutants.

Let's look at the options provided to determine which one is a source of water pollution.

• CFCs (Chlorofluorocarbons): CFCs are primarily known for their role in ozone depletion in the atmosphere. While they are greenhouse gases contributing to climate change, they are not typically classified as direct water pollutants in the context of runoff or discharge into water bodies.
• Washed out pesticides and fertilizers used in farming: Pesticides (chemicals used to kill pests) and fertilizers (substances added to soil to increase plant growth) are widely used in agriculture. When it rains, these chemicals can be washed off the fields and into nearby streams, rivers, lakes, and groundwater. This runoff, known as agricultural runoff, is a major source of water pollution. Pesticides can be toxic to aquatic life and humans, while excess fertilizers can lead to eutrophication, causing algal blooms that deplete oxygen and harm aquatic ecosystems.
• Gases released by vehicular traffic: Exhaust gases from vehicles, such as carbon monoxide (CO), nitrogen oxides (NOₓ), and hydrocarbons, are primary contributors to air pollution and the formation of smog. They do not directly cause water pollution.
• Smog: Smog is a type of air pollution formed by the reaction of pollutants like nitrogen oxides and volatile organic compounds in the presence of sunlight. It affects air quality and respiratory health but is not a direct cause of water pollution.

Based on the analysis, washed out pesticides and fertilizers from farming are a significant source of water pollution because they are carried into water bodies through runoff.

Therefore, the pollutant that causes water pollution among the given options is washed out pesticides and fertilizers used in farming.