Pollution has been among the biggest problems of the world today. Forget about big cities, even Grand Canyon is not immune to its negative effects. A new study has found that food webs of the canyon, a landmark of America's natural environment, have concentrations of mercury and selenium which are regularly exceeding their levels.

According to the study conducted by researchers from the United States Geological Survey (USGS), the exceeding levels of the concentrations could be hazardous for wildlife. Dr. David Walters, research ecologist at USGS and lead author of the study, said, "Managing exposure risks in the Grand Canyon will be a challenge, because sources and transport mechanisms of mercury and selenium extend far beyond Grand Canyon boundaries".

The researchers collected data from six different locations along the Colorado River to conduct the study published in the journal Environmental Toxicity and Chemistry. According to them, they were surprised to see that the concentrations of mercury and selenium in invertebrates, minnows and fish had surpassed the dietary toxicity levels.

According to the study, the average concentrations of mercury found in a number of fish during the study could make them harmful for humans to eat. Both mercury and selenium can be harmful for a human's health. High concentrations of mercury can affect the central nervous system, while selenium can cause problems like tooth and hair loss, or alertness problems. In some cases, high concentrations of selenium can result into liver tumors, according to the National Wildlife Federation.