Urolithiasis in railroad shopmen in relation to oxalic acid exposure at work

It is well known that the urinary excretion of oxalic acid is one of the main determinants for urinary stone formation. From 1950 to 1978 a saturated oxalic acid solution was used in a repainting and cleaning process for railroad cars in Norwegian railroad workshops. With the use of a questionnaire, the cumulative prevalence of urolithiasis-induced colic episodes was registered in the Sundland railroad depot. Forty-two (11.9%) out of 353 male workers not exposed to oxalic acid reported having had one or more such stone colic episodes. The corresponding figure for 15 individuals who had a very high exposure to oxalic acid was 8 (53.3%). Also workers in other departments, occasionally exposed to oxalic acid, had an increased stone colic prevalence rate, a finding suggesting a positive dose-response relationship. There was an increased frequency of stone colic episodes in the age group 40-69 years. Seven heavily exposed workers in the paint shop reported initial pollakiuria and slight dysuria during the exposure. The study indicates a causal relation between urinary stone formation in the investigated railroad shopmen and their exposure to oxalic acid at work.