Firstly, the production of chemical products can release harmful pollutants into the air, soil, and water. These pollutants can have serious consequences on human health, such as respiratory problems, cancer, and birth defects. By locating factories away from residential areas, these pollutants are less likely to enter nearby communities and pose a risk to residents' health.

Secondly, chemical plants can also release hazardous chemicals into the ground through spills or leaks. These chemicals can contaminate nearby water sources and harm aquatic life. In addition, they can also cause long-term damage to the soil and vegetation in the area, making it difficult for farmers to grow crops in the future. By keeping factories at least one kilometer away from residential areas, the risk of contamination is significantly reduced.

Thirdly, the production of chemical products can also produce noise pollution that can be harmful to human health. The constant noise from factory equipment and machinery can lead to hearing loss, stress, and other health problems. By ensuring that factories are located far enough away from residential areas, the noise levels are kept under control, reducing the negative impact on people's health.

In conclusion, the regulation requiring factories to be located at least one kilometer away from residential areas is an important measure to ensure public health and safety. It helps to minimize the risks of exposure to harmful pollutants, contamination of water sources and soil, and noise pollution. By following this rule, we can create a safer and healthier environment for ourselves and future generations.