Ground-level ozone levels in Shanghai, China were studied from 2010 to 2013 using a method called Differential Optical Absorption Spectroscopy. Ozone levels were highest in late spring and early summer, and lowest in winter. High ozone days were linked to transportation of volatile organic compounds and industrial emissions. High concentrations of HONO were found to increase ozone levels during pollution episodes. Overall, industrial activities and regional transport contribute significantly to ground-level ozone pollution in Shanghai.