Ambient Temperature and Occupational Injury Risk in US Surface Mining: A Nationwide Case-Crossover Analysis...

The temperature-injury exposure-response relationship in US mining remains uncharacterised using distributed-lag methods. A time-stratified case-crossover cohort was assembled of 106,838 injuries reported to the US Mine Safety and Health Administration (2005-2025) at 9,833 surface mines. Daily maximum temperature and dewpoint came from 4-km gridded climate data. A conditional-logistic distributed-lag nonlinear model was fit over lags 0-7, adjusted for dewpoint, precipitation and holidays. Relative to a minimum-morbidity temperature of 12.2 °C, risk was elevated at the 95th heat percentile (35.0 °C; relative risk [RR] 1.09, 95 % confidence interval [CI] 1.01-1.18). Cold-day effects were suggestive overall (RR at -7.9 °C 1.08, 95 % CI 0.97-1.20) but varied by subgroup. Falls showed a striking cold-day risk (RR 2.22, 95 % CI 1.71-2.89), the strongest of four cold-day subgroup associations surviving false-discovery-rate correction (falls at both cold percentiles, and the Southeast region and surface coal at the 1st percentile, the latter two narrowly); no heat-day subgroup association survived, and before multiplicity adjustment the Ohio Valley was the only region significant at both heat percentiles (RR 1.26, 95 % CI 1.06-1.49). The 95th-percentile association was robust, significant in eight of the nine specifications examined, whereas the 99th-percentile estimate (primary model RR 1.04, 95 % CI 0.93-1.16) was non-significant in every specification except the shortest lag window. Heat is therefore associated with a modest increase in overall injury risk; cold associations are subgroup-specific. These findings inform federal deliberations on occupational heat standards and support targeted cold-weather prevention.