Introduction Radon is a well-established human carcinogen, targeting the lung. A lot of epidemiological studies conducted on both uranium miners and general population in dwellings provided a risk quantification due to radon exposure, by alone and in combination with tobacco smoke. However, little is known about the risk due to combined exposure to radon and other occupational and environmental lung carcinogens.

Methods Literature review to identify the most critical scenarios of combined exposure to radon and other lung carcinogens, providing a framework for the risk assessment and addressing the planning of epidemiological studies.

Results The combined exposure to radon and other lung carcinogens may be relevant for several indoor working environments. However, it is important to keep in mind that for a number of workers a combined exposure may occur in a sequential way, i.e. to radon in indoor settings and to outdoor carcinogens if the job/s are conducted at least in part outdoor. Apart the tobacco smoke, co-exposures of interest include asbestos, crystalline silica, polycyclic aromatic hydrocarbons, hexavalent chromium, nickel and outdoor air pollution, all extensively assessed in both epidemiological and/or experimental studies.

Discussion Prevention of lung cancer occurrence in radon-exposed workers has not only to take into account the long-term indoor radon concentrations, as obtained by conventional dosimetric assessment, and the smoking status of the worker, but must include an accurate assessment of the patterns of exposure to other lung carcinogens, both ubiquitous and typical of a particular occupational or living setting. Unfortunately, validated biomarkers of exposure, early biological effect/s and individual susceptibility are not available in this regard and different lung carcinogens display different kinetics and may act through several distinct (although partly overlapping) cellular and molecular pathways, both genetic and epigenetic. The development of ‘omics’ approaches represent a promising tool to address this topic.