Independent report

Occupational risks for urolithiasis: IIAC information note

Published 26 April 2018

Background

1. A former seaman with long service in hot climes who had developed recurrent renal stones contacted the Industrial Injuries Advisory Council (IIAC) to enquire whether he was eligible to make a claim for Industrial Injuries Disablement Benefit (IIDB). The current list of prescribed diseases does not include renal stones.

2. Urolithiasis is the formation of stones anywhere in the upper urinary tract, the bladder, the ureters or the kidneys. Most stones originate in the kidney; they are often asymptomatic and are not uncommon, being detectable in around 8% of adults ^{[footnote 1]}.

3. Stones may cause pain (‘ureteric colic’) when they move from the kidney or obstruct the flow of urine. Acute ureteric colic is not uncommon with an annual incidence of 1-2 cases per 1000 people; an estimated 12% of men and 6% of women will have one episode of colic at some stage in their life, with the incidence peaking between 40-60 years for men and in the late 20s for women. Over 80% of urinary tract stones are passed spontaneously within a month and require no active treatment. Around two-thirds of men have ‘recurrent’ stones.

4. The frequency of urolithiasis is usually assessed through self-reports; the pain of ureteric colic is intense, and most people seek medical attention. Very few studies of occupational risk factors for stones have used objective methods of detection and most have reported measures of cumulative prevalence of episodes of colic.

5. ‘Disability’ as used in the context of the scheme would apply to the small proportion of individuals whose stones have caused significant renal or ureteric damage; and perhaps those with frequently recurrent episodes of colic.

Evidence

6. There appears to have been no published systematic review of occupational risk factors for urolithiasis but the council has undertaken one which it believes captures the bulk of the evidence, which is limited.

7. Several occupational associations have been described although, with the exception of those on workers poisoned by cadmium, few associations have been replicated. Frequently, the prevalence of stones in an occupational group has been estimated without an appropriate comparator, making it difficult to draw conclusions; these studies are not discussed further.

8. The evidence is a little stronger for two broad groups: those whose work entails exposure to renal toxins, and those working in hot, dehydrating atmospheres. Even for reports on these groups, analyses that control for potential confounding factors (for example, family history, diet) have rarely appeared.

Cadmium

9. Cadmium is a well-established renal toxin with lasting effects. Forty-six solderers in Sweden with heavy exposure to cadmium in 1978 were followed to 1993 by which time 10 had reported a history of renal stones. The prevalence was higher in those with higher levels of blood cadmium at the end of follow up ^{[footnote 2]}.

10. In all, 74 of 619 (12%) male employees of a Swedish battery factory, followed to 1990 (from 1931), reported kidney stones; the incidence was higher in those with higher estimated cumulative exposures to cadmium ^{[footnote 3]}.

11. In a cohort of 27 coppersmiths in Glasgow, with chronic exposure to cadmium and after six years of follow-up, the cumulative prevalence of stones was 40%; this was compared to a point prevalence of 3.5% in an unexposed working population ^{[footnote 4]}.

Other chemical exposures

12. Trimethyltin is a chemical used in the manufacture of PVC. Of 216 male employees of a plastics factory in China, screened by renal ultrasound, 18% had a kidney stone, a proportion higher than in a referent group of 119 employees (6%) of another factory without exposure ^{[footnote 5]}

13. Between 1950 and 1978 a saturated solution of oxalic acid was used in Norway to clean railway carriages prior to repainting. The cumulative prevalence of renal colic in 15 men with high exposure was 53%, compared to 12% in 353 co-workers without exposure ^{[footnote 6]}.

14. Silkscreen workers who are exposed to ethylene glycol ethers and their acetates have changes in their urinary chemistry which might predispose them to the formation of renal stones ^{[footnote 7]}. The incidence of stones in this population appears not to have been measured, however.

Work at high ambient temperatures

15. The council is aware of a few studies of ‘hot’ work in which there are helpful estimates. In one ^{[footnote 8]}, 10,326 Brazilian steel mill workers were surveyed. In 1,289 ‘hot workers’ (working in temperatures between 50°C and 150°C) the cumulative prevalence of renal stones was 8%, higher than among the other workers (1%).

16. Among 236 machinists, working at high temperatures in an Italian glass factory, the prevalence of renal stones was 8.5%; the equivalent figure in 165 other employees, working at normal temperatures, was 2.4% (p=0.03). A high rate (39%) of uric acid stones was present in the workers ‘exposed to heat stress’ ^{[footnote 9]}.

17. Two-thirds of 38 men in Glasgow with symptomatic stones had occupational exposure to ‘hot metals’; this was higher than the proportion (maximum 26%) in a local referent population ^{[footnote 10]}.

18. A questionnaire survey was carried out to determine the prevalence of urinary stone disease in 406 male workers in several occupations in Singapore. The prevalence was five times higher in outdoor workers (5.2%) compared to indoor workers (0.85%, p<0.05) ^{[footnote 11]}.

19. We have found only one informative publication relating to seamen. In a survey of 350 Royal Navy personnel with radiologically or surgically confirmed urolithiasis between 1958 and 1964, the estimated cumulative prevalence among non-officers was highest (but not so much as doubled) in engineers and cooks, described as the two occupations working in especially high temperatures ^{[footnote 12]}. In all personnel, the rates were highest in those who had served in the Middle or Far East.

Conclusions

20. It is probable that both work with some renal toxins and work in hot, dehydrating environments increase the risk of urolithiasis but the evidence base is currently small and methodologically weak, and therefore insufficient for the council to recommend prescription.

Prevention note

The Health and Safety Executive provides advice on how to avoid heat stress at work in high ambient temperatures (PDF).

 

29 March 2018

  

References

1. Boyce CJ, Pickhardt PJ, Lawrence EM, Kim DH, Bruce RJ. Prevalence of urolithiasis in asymptomatic adults: objective determination using low dose noncontrast computerized tomography. J Urol. 2010;183(3):1017-21. ↩

2. Jarup L, Persson B, Elinder CG. Blood cadmium as an indicator of dose in a long-term follow-up of workers previously exposed to cadmium. Scandinavian journal of work, environment & health. 1997;23(1):31-6. ↩

3. Jarup L, Elinder CG. Incidence of renal stones among cadmium exposed battery workers. British journal of industrial medicine. 1993;50(7):598-602. ↩

4. Scott R, Cunningham C, McLelland A, Fell GS, Fitzgerald-Finch OP, McKellar N. The importance of cadmium as a factor in calcified upper urinary tract stone disease–a prospective 7-year study. Br J Urol. 1982;54(6):584-9. ↩

5. Tang X, Li N, Kang L, Dubois AM, Gong Z, Wu B, et al. Chronic low level trimethyltin exposure and the risk of developing nephrolithiasis. Occupational and environmental medicine. 2013;70(8):561-7. ↩

6. Laerum E, Aarseth S. Urolithiasis in railroad shopmen in relation to oxalic acid exposure at work. Scandinavian journal of work, environment & health. 1985;11(2):97-100. ↩

7. Laitinen J, Liesivuori J, Savolainen H. Urinary alkoxyacetic acids and renal effects of exposure to ethylene glycol ethers. Occupational and environmental medicine. 1996;53(9):595-600. ↩

8. Atan L, Andreoni C, Ortiz V, Silva EK, Pitta R, Atan F, et al. High kidney stone risk in men working in steel industry at hot temperatures. Urology. 2005;65(5):858-61. ↩

9. Borghi L, Meschi T, Amato F, Novarini A, Romanelli A, Cigala F. Hot occupation and nephrolithiasis. J Urol. 1993;150(6):1757-60. ↩

10. Ferrie BG, Scott R. Occupation and urinary tract stone disease. Urology. 1984;24(5):443-5. ↩

11. Pin NT, Ling NY, Siang LH. Dehydration from outdoor work and urinary stones in a tropical environment. Occupational medicine (Oxford, England). 1992;42(1):30-2. ↩

12. Blacklock NJ. The pattern of urolithiasis in the Royal Navy. J R Nav Med Serv. 1965;51(2):99-111. ↩