In terms of water quality, pathogens can significantly affect:

Pathogens, which include bacteria, viruses, and protozoa, pose a significant risk to human health when present in water. They can cause a range of illnesses, from mild gastrointestinal issues to severe diseases, depending on the type of pathogen and the susceptibility of the individual exposed. Contaminated water sources are a major concern for water quality and public health, especially in drinking water systems. Monitoring and controlling pathogen levels in water is essential to ensure safe drinking water and prevent waterborne diseases, making human health the crucial aspect influenced by the presence of pathogens in water.

While water hardness, biochemical oxygen demand, and pH levels are important water quality parameters, they are not directly influenced by pathogens. Water hardness relates to the concentration of minerals like calcium and magnesium, biochemical oxygen demand measures the amount of organic matter in the water, and pH levels indicate the acidity or alkalinity of the water. These factors may influence the overall quality of water, but they do not directly address the threat to human health posed by pathogens. Therefore, focusing on the impact of pathogens emphasizes their direct connection to health risks associated with water quality.