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Tatjana Dizdarevic, B.S.M.E. Idrija Mercury Mine

Idrija, march 2003. HEALTH SAFETY PROGRAMME FOR WORKERS EXPOSED TO HG° ENVIRONMENTAL POLLUTION IN THE IDRIJA REGION AND OVER A BROAD AREA. Tatjana Dizdarevic, B.S.M.E. Idrija Mercury Mine. Idrija. Introduction. Mercury was discovered in y. 1490 500 years of mining and smelting

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Tatjana Dizdarevic, B.S.M.E. Idrija Mercury Mine

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  1. Idrija, march 2003 HEALTH SAFETY PROGRAMME FOR WORKERS EXPOSED TO HG° ENVIRONMENTAL POLLUTION IN THE IDRIJA REGION AND OVER A BROAD AREA Tatjana Dizdarevic, B.S.M.E. Idrija Mercury Mine

  2. Idrija

  3. Introduction • Mercury was discovered in y. 1490 • 500 years of mining and smelting • In y. 1994 the ore excavation and Hg production stoped • The Mine will be shut down in 2006

  4. Important data • Hg content in ore: 0,1 – 10% • monomineral ore deposit: 70% HgS and 30%Hg • 12 mill. tons of ore was excavated • 153.309 tons of Hg was extracted • 107.692 tons of commercial Hg • losses: 44.616 tons of Hg

  5. Closing-down Programme • The Long-term closing down Programme for the gradual, complete and permanent shut down of the Idrija Mine was prepared in 1986, addopted in 1987 and approved in 1989 • The results of investigations and closing down works through last few years indicate that the concept of the mine’s shutdown, was wll chosen •  thus ensuring the safety of the town above the pit

  6. Closing-down works in the mine • gradually from the lowest level upwards towards the surface • backfilling(20.512 m of galleries, 120.785 m3 concrete) • injecting (37 locations  43.856 m of boreholes, 70.177 m3 of grout) • flooding of the pit (up to the 4th level)

  7. WORKING LOADS AND MERCURY CONCENTRATIONS IN THE PIT AND IN THE SMELTING PLANT Physical loads 5 - 9 Kcal.min-1 • (dynamic and static) • Pulmonal ventilation 24 - 33 L air.min-1 • Air temperature 15 - 30 oC • Relative humidity 70 - 92 % • Effective temperature 15 - 27.8 • Dust concentration 30 - 70 mg.m-3 • (respirable part) • % free SiO2 in dust 10 - 30 % • Ionising radiation • Gama dose-rate • Carboniferous shale 0.15 -0.20 Gy.h-1 • Bituminous shale up to 1 Gy.h-1 • Radon concentrations 700 - 1500 Bq.m-3 • Radon daughters 1.5 J.m-3 (0.07 WL)

  8. WORKING LOADS AND MERCURY CONCENTRATIONS IN THE PIT AND IN THE SMELTING PLANT Mercury concentrations in the pit and in the smelting plant The pit cinnabar ore (HgS) excavations 0.10 mgHg0.m-3 native mercury ore excavations 0.10 - 1.00 2.00 mgHg0.m-3 The smelting plant “less hazardous jobs” 0.00-0.10 mgHg0.m-3 “more hazardous jobs”  0.10 -2.50  3.00 mgHg0.m-3 Type of workers’ exposure intermittent workers’ exposure to high Hgo concentr.

  9. MAJOR PROBLEMS RELATED TO THE TECHNICAL AND HEALTH PROTECTION OF MINERS AGAINST MERCURY HAZARDS IN THE PERIOD BEFORE 1964 • In this period Hg concentrations (mg.m-3) were not regularly monitored at all workplaces in mine areas with native Hg by means of measurements; • workers were assigned to workplaces with increased Hg concentrations without consideration for their previous exposure to Hg; • deficient technical protective measures; • workers did not use personal safety equipment; • the Technical Service assigned workers to workplaces with increased Hg concentrations without consulting the Health Service; • the Health Service did not monitor the state of health of workers during regular exposure; • health supervision did not include biological monitoring.

  10. HEALTH AND SAFETY PROGRAMME FOR WORKERS EXPOSED TO ELEMENTAL MERCURY AT THE IDRIJA MERCURY MINE(Kobal, Dizdarevič, 1997) • Regular monitoring of mercury concentrations at workplaces in the pit and smelting plant; • Improvement of technical measures for the reduction of mercury concentrations at workplaces in areas with native mercury; • Continuous use of personal safety equipment by workers exposed to mercury; • Regular and controlled rotation of workers from hazardous to nonhazardous workplaces and reduction of their exposure to mercury from 8 to 6 and even 4 hours daily; • Regular monitoring of external exposure of individual workers and estimation of cumulative monthly external exposure; • Medical surveilance and estimation of workers’ specific ability for work at workplaces with increased concentrations of Hg vapours.

  11. CONTROL OF WORKING ENVIRONMENT Air Measurements and Mercury Emission Controls Instant reading methods(quantification of mercury vapours): Mercury vapour Meter - Beckmann K-23 range 0.005-0.1 mg.m-1, and 0.003-3.0 mg.m-3 repeatability + 10% Mercury vapour Indicator - MVI Shawcity range 0.00 - 2.00 mg.m-3, sensitivity 1g.m-3 repeatability + 5 % Methods with separate sampling(quantification of total mercury): acido-oxidising media (KMnO4), hopcalite, activated charcoal, gold traps. Samples are analised with cold vapour atomic absorbtion spectrometrie(CVAAS) and with neutronic activation analizes(NAA).

  12. TECHNICAL PRECAUTIONS Ventilation This technical measure includes: efficient front area ventilation and indirectly a reduction of the temperature of air in the pit. Q  300 - 400 m3 air ..... air quantitiy F  10 m2 .... the cross-section of mine’s gallery T ... (oC) as low as possible (the temperature of the input air) l = 4F .... (m) the distance between the front area and the ventilation pipe

  13. TECHNICAL PRECAUTIONS Ore processing technology • Developement of a new underhand mining method with cemented backfill for extracting mercury ore from carboniferous shale containing native mercury. • With the introduction of a new method of excavation, the mercury concentrations in the pit air decreased for about 30%. • The reduction of the active vaporization surface reduces the emission of vaporized mercury, which essentialy contributes to the reduction of mercury concentrations in pit air.

  14. TECHNICAL PRECAUTIONS Calcium polysulphide solution (CaSn) Hg + CaSn HgS + CaSn-1

  15. TECHNICAL PRECAUTIONS Personal protection equipment • introduction of mask with mercury vapour filter for hazardous works in the smelting plant after 1952; • use of isolating apparatures in particularly hazardous works; • after 1965 the introduction of Drger half-masks with M 105 St. filters at all workplaces in the pit where Hg concentrations in air exceeded 0.1 mg.m-3; • in 1984 AH6-Airstream Racal safety helmets with AS60502 filters comprised of two layers of active charcoal began to be used at all workplaces with increased concentrations of Hg vapours.

  16. TECHNICAL PRECAUTIONS Personal safety equipment Air-purifing helmet AH6-Airstream, RACAL, with mercury absorbing filter Calculation of useful life of filter AS60502 (estimation of load): The cumulative load is: Bmax = cn tn cn ....... daily concentrations of Hg vapours tn ...... duration of filter’s(miner’s) exposure to a certain Hg concentration When 1200 points are attained, the filter is to be replaced.

  17. EXTERNAL MONTHLY EXPOSURE INTENSITY(AMI) The Allowable Monthly exposure Intensity (AMI) is determined on the basis of the assumption that a worker can work in an area with concentrations of Hg vapours up to 0.1 mg.m-3 air without safety equipment for a period of 8 hours daily for an average period of 26 days (the basis of calculating AMI was the maximum allowable daily exposure to Hg): AMI = 0.1 mg.m-3 8 hours  26 days/month = = 20.8 points The allowable monthly exposure intensity is thus assessed at 20.8 points, which a worker is not allowed to exceed while working in hazardous areas. In practise, the mine’s Technical Service calculated the monthly allowable exposure time (MI) in the following way: MI =  cn tn cn ....... daily concentrations of Hg vapours tn ....... duration of miner’s exposure to a certain Hg concentration

  18. MEDICAL SURVEILLANCE OF WORKERS EXPOSED TO ELEMENTAL MERCURY Target medical examination (screening test) • Evaluation of typical nonspecific symptoms and signs (related to “micromercurialism”); • Evaluation of current health contraindications to Hg exposure; • Timing of evaluation: before, during (once per week) and after exposure. External exposure evaluation • Annual exposure data • (time, concentration, Alowable Monthly exposure Intensity - AMI); • Current exposure data • (time, concentration, Monthly exposure Intensity- MI); • Timing of evaluation: before, during and after exposure.

  19. MEDICAL SURVEILLANCE OF WORKERS EXPOSED TO ELEMENTAL MERCURY Biological monitoring • Cumulative internal dose evaluation Urine mercury: morning urine, 18 or 24-hour urine samples; timing of evaluation: before exposure. • Current internal dose evaluation Urine mercury: post-shift urine spot samples; timing of evaluation: during exposure 1 - 2 times per week; Blood mercury (workplaces with high mercury concentrations); timing of evaluation: during exposure - at the end of the week.

  20. MEDICAL SURVEILLANCE OF WORKERS EXPOSED TO ELEMENTAL MERCURY Biological monitoring • Our recommended temporary Health based Biological Limit Value (BLV) • BLV for workers intermittently exposed to Hg - 4 hours per day at average pulmonal ventilation 27 L.min-1 (Kobal 1991). • Blood mercury: 35 g/L • Urine mercury*: 60 g/L • at 68% confidence limit 100 g/L** (upper limit) • at 95% confidence limit 135 g/L** (upper limit) _______________________ * Correction of urine mercury concentration for specific gravity 1024 (Barber, Wallis 1986). ** U-Hg prediction based on B-Hg value 35 g/L, yU-Hg= 1.35 x + 14.3, r = 0.68, P = 0.000, standard error of predictions sy= + 37.7 g/L.

  21. Environmental pollution The realities of mercury pollution • The ecolgical flap over mercury poisoning has already cut deeply into the metal’s traditional markets …. • Lesson of Minamata Disease • Mercury Contamination in Iraq • Mercury Contamination in the Amazon (Another Minamata?)

  22. Environmental pollution in Idrija Region (monitored since 1970) • Hg in air • Hg in water • Hg in sediments • Hg in soil • Hg in plants • Hg in animals • Hg in humans • Hg in old dust

  23. Environmental pollution in Idrija Region 500 years of mining activity  3.000.000 m3 of ore and gangue  total production of 150.000 tons of Hg • 110.000 tons (commercial Hg ) • 40.000 tons (disipated into the environment, i.e. 20 kg Hg/day)

  24. Hg production in Idrija Mercury Mine 1490 - 1995(Mlakar 1974, Cigale 1997) Total Hg production in Idrija Mercury Mine 1490 - 1995(Cigale 1997)

  25. Average mercury concentrationsin the air in Idrija

  26. Distribution of Mercury in the Athmosphere over Idrija (M. Gosar et al., 1997)

  27. Average mercury concentrations in soil in Idrija(mgHg/kg)

  28. Hg in soil(Gosar M., PHD thesis, 1997)

  29. Pollution of Pit and Surface Waters

  30. Mercury (dissolved) in the Surface Water of Gulf of Trieste(M. Horvat et al. Sept. 1995, surface water,)

  31. Smelting plant1860 - 1970

  32. Smelting plant1980 - 1995

  33. Mercury in Air - smeltery *the limit value of Hg in air for residential areas

  34. Smelting plant today

  35. Remediation

  36. Pront area – outcrop of ore deposit

  37. Pront area (1999)

  38. Mercury in plants

  39. Mercury in animals tissues

  40. Conclusions • Results  • Environment rehabilitation measures • Reduction of loads on the population

  41. GOOD LUCK

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