Objective To investigate the short-term effect of air temperature on outdoor occupational injuries (out_OI) in Central Italy, also by taking different geographical factors and employment sectors of workers into account.

Methods Out_OI for all of Tuscany (Central Italy), from 2003 to 2010 (n=162 399), were provided by the National Institute of Insurance for Occupational Illness and Injury. Representative daily meteorological data of the geographical area under study were obtained from the European Reanalysis-interim climatological reanalysis archive. Relationships between short-term changes in air temperature and out_OI were studied through Generalised Additive Models.

Results The exposure-response curves of out_OI and short-term changes in air temperature generally showed significant out_OI increases when cold conditions occurred. The air temperature breakpoint corresponded to the 10th centile (−0.8°C) of the air temperature time series used in this study: a 1°C decrease in temperature below the 10th centile corresponded to a 2.3% (CI 1.3% to 3.3%) increase of out_OI throughout all of Tuscany. The cold effect was strongest in plain areas, especially when out_OI occurred in vehicles other than cars. No relationships of injuries with temperature extremes were observed in workers who generally spend half or most of their time outdoors, such as construction, land and forestry workers. However, these latter outdoor workers showed significant linear associations of injuries with typical (far-from-extreme) temperatures.

Conclusions This large population-based study highlights the significant and independent effects of short-term air temperature changes (especially cold) in triggering out_OI. These findings represent the first step towards developing a geographically differentiated, operative outdoor-temperature-occupational-health warning system aimed at preventing outdoor work injuries.