Calf Muscles. 1  The calf muscles are six in number: the gastrocnemius, the soleus, the popliteus, the tibialis posterior, the flexor digitorum longus, and the flexor hallucis longus. 2  The gastrocnemius and the soleus run between the knee and the ankle. 3  One of the calf muscles, the soleus, has a special ability.
Ozone Pollution. Ground level or bad ozone is not emitted directly into the air, but is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight.
Precursors of Photochemical Smog. Ozone, the most common chemical in urban smog, is the result of a complex photochemical reaction between nitrogen oxides and hydrocarbons. The main source of nitrogen oxide pollution is motor vehicle exhaust, according to the Environmental Protection Agency.n the early 1900's, the British coined the term 'smog' to describe the thick, sulfuric smoke that spewed from London's industrial chimneys and hung in the fog. Today's smog also contains sulfur, but the major chemical in fog is ground-level ozone, according to the Environmental Protection Agency.