The near infrared (IRA, 780–1.400 nm) represents a primary component of the solar spectrum, accounting for about 30% of the total solar energy reaching the soil. IRA is highly penetrating, being able to reach the subcutaneous tissues. Moreover, significant amounts of IRA may reach retinal tissue. Outdoor workers are occupationally exposed to solar radiation. However, until now the attention was primarily focused on the acute and long-term adverse effects (especially skin cancer) involving both skin and eyes due to UVB and UVA bands.Methods
A literature search was conducted to assess the current knowledge about the biological effects of IRA, analysing implications in terms of occurrence of long term adverse effects in people working outdoor.Results
Experimental studies show that IRA may affect gene expression profile and the redox balance of the cell, especially fibroblasts, causing a direct or an indirect increase in ROS production, primarily interfering with mitochondrial activity. Until now there is no epidemiological evidence regarding long-term adverse effects due to solar IRA, by alone or in combination with other bands of solar radiation.Discussion
The available data suggest that IRA may have biological effects regardless of the potential temperature increase of tissues. Moreover, a synergistic action between IRA, visible radiation, UVB or UVA, may not be excluded, for instance regarding ROS production, modulation of cell signalling, induction of mutations and/or epigenetic changes, especially for prolonged and repeated exposures of skin and eye tissues. Waiting for new experimental and epidemiological data (including those obtained applying ‘omics’ technologies) protection of workers exposed to solar radiation should ideally include the shielding of IRA (although effective sunscreens are not yet available in this regard), while health surveillance should not ignore the possibility of synergistic effects. Finally, preventive pathways have to include, among others, education to healthy lifestyles.