Meaning of PHOTOCHEMICAL in English
[adjective] [not gradable] [specialized] - relating to the effect of light on some chemicalsOzone, produced by the photochemical reaction of sunlight with unburnt hydrocarbons, and carbon monoxide emissions are rising inexorably.A photochemical smog is a fog caused by light from the sun shining on some types of chemicals in the air in areas with a lot of industry and traffic.Photochemical smogs are worse in summer, when the sun's rays on the cloud of traffic fumes produce a photochemical reaction, creating high levels of ozone.
Cambridge English vocab. Кембриджский английский словарь. 2012