Photochemical smog is primarily composed of ozone ($\text{O}_3$) and nitrogen oxides ($\text{NO}_x$), along with peroxyacetyl nitrate (PAN), volatile organic compounds (VOCs), and particulate matter. $\text{NO}_x$ and hydrocarbons from vehicle emissions react in sunlight to produce ground-level ozone and secondary pollutants. PAN (not PPN) is also a component. Both $\text{O}_3$ and $\text{NO}_x$ are the major oxidant components of photochemical smog.