A thick fog sweeping across northern California and Oregon is posing a threat to the ecological chain. It may not be harmful to humans, but it can be harmful to plants and other animals.

Popular Science reports that the amount of coastal fog in some areas of California contains an unexpected amount of mercury called monomethylmercury. During the American Geophysical Union's fall meeting, researchers discussed possible implications of these findings. While it is true that monomethylmercury can be hazardous to human health, there isn't enough in the fog that can directly affect humans.

Clive Dorman from San Diego State University analyzed the records of ships in coastal areas in northern California and Oregon. He was able to conclude that the number of days with fog went up by 7.4 percent between 1960 and 2007. The same trend can be seen in other parts of the world.

The increase doesn't jut concern coastal navigation but also the whole ecosystem. Kenneth Caole ofMoss Landing Marine Laboratories and Peter Weiss-Penzias from UC Santa Cruz discovered that levels of monomethylmercury were 19 times higher in fog than in rain.

This is can be a major public health concern. This type of mercury is linked to different types of health issues including kidney failure, birth defects and neurological impairment.

Emissions from smokestack and other industrial plants contribute to the mercury found in the ocean. This substance is being absorbed by animals which get eaten by carnivores. In turn, the carnivores build up large amount of monomethylmercury as it consumes many mercury-contaminated preys.  

The levels of mercury in the fog may not be that high to call an immediate public health risk however, high concentrations are already found in terrestrial plants and animals. This can create a negative impact on land-based food chain. Spiders were found to have more mercury levels than FDAs accepted limit.

Although spiders are not part of our food options, in other animals they are. The team is trying to further study the possible implications of high levels of mercury on land food chain.