What is pea soup fog and where is it found?

Pea soup fog is a very thick fog that can sometimes have a dark green hue, which is where it gets its name. Today, it is usually only found in parts of Bolivia and Brazil, but can also be seen in other parts of South America, including the Amazon Basin. Other than its outward appearance it is not unlike other fog, except that it can appear very quickly, and can be dangerous if inhaled.