TLVs for heat stress

1. Mike Slater

2. Threshold Limit Values ® (TLVs) for heat stress are included in the American Conference of Governmental Industrial Hygienists (ACGIH) TLV booklet

3. TLVs® are guidelines designed for use by occupational hygienists in making decisions regarding safe levels of exposure to various chemical substances and physical agents found in the workplace.

4. This flowchart summarises how to apply the TLV’s. However. It’s quite complex. We’ll go through it step by step

5. General approach Detailed Heat Strain Screening Analysis Monitoring

6. General approach Detailed Heat Strain Screening Analysis Monitoring

7. Heat Stress NO STOP expected? YES SCREENING

8. Screening NO Clothing adjustment factors available? YES

9. TLV Clothing Corrections Clothing Type WBGT Correction Work clothes (long sleeve and pants) 0 Cloth (woven material) coveralls 0 Double layer woven clothing 3 SMS polypropylene coveralls 0.5 Polyolefin overalls 1 Limited use vapour-barrier overalls 11

10. Screening NO Clothing adjustment factors available? YES If no clothing adjustment factors are available, go straight to heat strain (physiological) monitoring

11. Screening NO Clothing adjustment factors available? YES This may be necessary, for example, where chemical protective suits are being worn

13. Screening NO Clothing adjustment factors available? YES Are screening NO criteria for Action Limit exceeded? YES

14. Work out the WBGT from the results of environmental measurements and apply the clothing corrections

15. WBGT Index No direct exposure to sunlight WBGT = 0.7 tnwb + 0.3 tg With direct exposure to sunlight WBGT = 0.7 tnwb + 0.2 tg + 0.1 ta

16. Compare the corrected WBGT with the Action Limit Values

17. ACGIH TLVs – Action Limit Allocation of Workload work in work Light Moderate Heavy V ery cycle heavy 75% to 100% 28.0 25.0 - - 50% to 75% 28.5 26.0 24.0 - 25% to 50% 29.5 27.0 25.5 24.5 0 to 25% 30.0 29.0 28.0 27.0

18. To use this table you have to know • the time spent working and resting • the metabolic rate

19. Metabolic rate categories Category Metabolic Examples Rate (W) Sitting Rest 115 Sitting or standing Light 180 Light hand / arm work Walking Moderate 300 Moderate lifting Heavy materials handling Heavy 415 Pick and shovel work Very Heavy 520

21. So, for a job involving moderate work where 75% of the time is spent working and 25% resting

26. ACGIH TLVs – Action Limit Allocation of Workload work in work Light Moderate Heavy V ery cycle heavy 75% to 100% 28.0 25.0 - - 50% to 75% 28.5 26.0 24.0 - 25% to 50% 29.5 27.0 25.5 24.5 0 to 25% 30.0 29.0 28.0 27.0 If the adjusted WBGT is below this value the Action Limit is not exceeded

27. Screening NO Clothing adjustment factors available? YES Are screening NO criteria for Action Low Risk Limit exceeded? YES

28. Screening NO Clothing adjustment factors available? YES Are screening NO Continue work criteria for Action Low Risk Monitor Limit exceeded? YES

29. Screening NO Clothing adjustment factors available? YES Are screening NO Continue work criteria for Action Low Risk Monitor Limit exceeded? YES NO If the Action Limit is Are screening exceeded then the WBGT criteria for TLV exceeded? value is compared with the TLV criteria YES

30. ACGIH TLVs – Screening TLV Allocation of Workload work in work Light Moderate Heavy V ery cycle heavy 75% to 100% 31.0 28.0 - - 50% to 75% 31.0 29.0 27.5 - 25% to 50% 32.0 30.0 29.0 28.0 0 to 25% 32.5 31.5 30.5 30.0

31. Screening NO Clothing adjustment factors available? YES Are screening NO Continue work criteria for Action Low Risk Monitor Limit exceeded? YES Are screening NO Implement criteria for TLV general exceeded? controls YES

32. General Information, instruction & training controls Regular drinks of water Self regulation Health screening and surveillance Encourage reporting symptoms Encourage healthy lifestyles Monitoring

33. Screening NO Clothing adjustment factors available? YES Are screening NO Continue work criteria for Action Low Risk Monitor Limit exceeded? YES Are screening NO Implement Continue work criteria for TLV general Maintain controls exceeded? controls Monitor YES

35. Detailed analysis NO Are data available for detailed analysis? YES If the TLV is exceeded, consider carrying out a more detailed analysis using a more sophisticated method, such as the Predicted Heat Strain (PHS) index

36. Detailed analysis NO Are data available for detailed analysis? YES NO Action Limit exceeded? YES

37. The Action Limit referred to here is that associated with the index being used NOT the ACGIH Action Limit

38. Detailed analysis NO Are data available for detailed analysis? YES NO Action Limit exceeded? YES

39. Detailed analysis NO Are data available for detailed analysis? YES NO Action Limit Low Risk exceeded? YES

40. Detailed analysis NO Are data available for detailed analysis? YES NO Action Limit Continue work Low Risk exceeded? Monitor YES

41. Detailed analysis NO Are data available for detailed analysis? YES NO Action Limit Continue work Low Risk exceeded? Monitor YES NO TLV exceeded? YES

42. The TLV referred to here is the limit value associated with the index being used NOT the ACGIH Screening TLVs

43. Detailed analysis NO Are data available for detailed analysis? YES NO Action Limit Continue work Low Risk exceeded? Monitor YES NO TLV exceeded? YES

44. Detailed analysis NO Are data available for detailed analysis? YES NO Action Limit Continue work Low Risk exceeded? Monitor YES NO Implement TLV exceeded? general controls YES

45. Detailed analysis NO Are data available for detailed analysis? YES NO Action Limit Continue work Low Risk exceeded? Monitor YES NO Implement Continue work TLV exceeded? general Maintain controls controls Monitor YES

46. Heat strain monitoring NO Implement Continue work TLV exceeded? general Maintain controls controls Monitor YES What if the TLV is exceeded?

47. Heat strain monitoring NO Implement Continue work TLV exceeded? general Maintain controls controls Monitor YES Perform heat strain (physiological) monitoring

48. Physiological assessment Core Temperature Heart rate

49. Personal Monitor

50. Miner’s Core Temperature & Heart Rate Source: OHTA.

51. Heat strain monitoring NO Implement Continue work TLV exceeded? general Maintain controls controls Monitor YES Perform heat strain (physiological) monitoring Excessive heat NO strain based on monitoring? YES

52. Guidelines for limiting Heat Strain Factor Work should be discontinued if: Heart rate (beats per minute) Greater than 180 minus age in years Core temperature Greater than 38.5 0C (acclimatised) Greater than 38.0 0C (unacclimatised) Recovery heart rate 120 (beats per minute) (at one minute after peak work) Other Symptoms of sudden and severe fatigue, nausea, dizziness or lightheadedness

53. Heat strain monitoring NO Implement Continue work TLV exceeded? general Maintain controls controls Monitor YES Perform heat strain (physiological) monitoring Excessive heat NO strain based on monitoring? YES

54. Heat strain monitoring NO Implement Continue work TLV exceeded? general Maintain controls controls Monitor YES Perform heat strain (physiological) monitoring Excessive heat NO strain based on monitoring? YES Implement Job- specific controls

55. Job-specific controls Engineering controls Administrative controls Personal protective equipment

60.  At workstation  Ta = 24 0C  Tw = 22 0C  Tg = 28 0C  V = 0.4 m/s Work involves monitoring process Minimal manual effort required Standard overalls worn

61. WBGT Index No direct exposure to sunlight WBGT = 0.7 tnwb + 0.3 tg With direct exposure to sunlight WBGT = 0.7 tnwb + 0.2 tg + 0.1 ta

62.  At workstation  Ta = 24 0C  Tw = 22 0C  Tg = 28 0C  V = 0.4 m/s WBGT = 23.8 0C

66. Metabolic rate categories Category Metabolic Rate (W) Rest 115 Light 180 Moderate 300 Heavy 415 Very Heavy 520

68. ACGIH TLVs – Action Limit Allocation of Workload work in work Light Moderate Heavy V ery cycle heavy 75% to 100% 28.0 25.0 - - 50% to 75% 28.5 26.0 24.0 - 25% to 50% 29.5 27.0 25.5 24.5 0 to 25% 30.0 29.0 28.0 27.0 WBGT = 23.8 0C

69. Screening NO Clothing adjustment factors available? YES Are screening NO criteria for Action Low Risk Limit exceeded? YES

70. Screening NO Clothing adjustment factors available? YES Are screening NO Continue work criteria for Action Low Risk Monitor Limit exceeded? YES

72. Boiler Cleaning Air Wet Globe Air temp. bulb temp. velocity (0C) temp. (0C) (m/s) (0C) Start of work 34 19 51 0.2 After 5 hours 32.5 18.5 51.5 0.2 Heavy manual effort required Standard overalls worn

73. Boiler Cleaning Air Wet Globe Air temp. bulb temp. velocity (0C) temp. (0C) (m/s) (0C) Start of work 34 19 51 0.2 After 5 hours 32.5 18.5 51.5 0.2 WBGT = 28.6 0C

80. ACGIH TLVs – Action Limit Allocation of Workload work in work Light Moderate Heavy V ery cycle heavy 75% to 100% 28.0 25.0 - - 50% to 75% 28.5 26.0 24.0 - 25% to 50% 29.5 27.0 25.5 24.5 0 to 25% 30.0 29.0 28.0 27.0 WBGT = 28.6 0C So Action Limit is exceeded

81. Screening NO Clothing adjustment factors available? YES Are screening criteria for Action Limit exceeded? YES Are screening NO criteria for TLV exceeded? YES

83. ACGIH TLVs – Screening TLV Allocation of Workload work in work Light Moderate Heavy V ery cycle heavy 75% to 100% 31.0 28.0 - - 50% to 75% 31.0 29.0 27.5 - 25% to 50% 32.0 30.0 29.0 28.0 0 to 25% 32.5 31.5 30.5 30.0 WBGT = 28.6 0C So TLV is NOT exceeded provided work is restricted to 50% of shift

84. Screening NO Clothing adjustment factors available? YES Are screening NO Continue work criteria for Action Low Risk Monitor Limit exceeded? YES Are screening NO Implement criteria for TLV general exceeded? controls YES

85. Reduce risk  Allow boiler to cool down before starting work

86. Working methods  Mechanical aids  Self pacing

87. Manage exposure time  Implement work:rest regime  Work restricted to 25% to 50% of work cycle

88. Provide information, instruction and training  Risks  Good working practice  Symptoms to look out for

89. Provide water  Drink at regular intervals

90. Health surveillance  Pre-placement medical screening  Regular health checks  Encourage reporting of symptoms

91. Encourage healthy lifestyle  Diet  Exercise  Moderate alcohol consumption

94. Furnace Repair Air Wet bulb Globe Air temp. temp. temp. velocity (0C) (0C) (0C) (m/s) 98 45 150 1 Heavy manual effort required Thick, woollen clothing worn

95. Furnace Repair Air Wet bulb Globe Air temp. temp. temp. velocity (0C) (0C) (0C) (m/s) 98 45 150 1 WBGT = 76.5 0C

98. Furnace Repair Air Wet bulb Globe Air temp. temp. temp. velocity (0C) (0C) (0C) (m/s) 98 45 150 1 Corrected WBGT = 79.5 0C

102. ACGIH TLVs – Action Limit Allocation of Workload work in work Light Moderate Heavy V ery cycle heavy 75% to 100% 28.0 25.0 - - 50% to 75% 28.5 26.0 24.0 - 25% to 50% 29.5 27.0 25.5 24.5 0 to 25% 30.0 29.0 28.0 27.0 Corrected WBGT = 79.5 0C So Action Limit is exceeded

103. Screening NO Clothing adjustment factors available? YES Are screening criteria for Action Limit exceeded? YES Are screening NO criteria for TLV exceeded? YES

105. ACGIH TLVs – Screening TLV Allocation of Workload work in work Light Moderate Heavy V ery cycle heavy 75% to 100% 31.0 28.0 - - 50% to 75% 31.0 29.0 27.5 - 25% to 50% 32.0 30.0 29.0 28.0 0 to 25% 32.5 31.5 30.5 30.0 Corrected WBGT = 79.5 0C So TLV is exceeded

106. Are screening criteria for TLV exceeded? YES NO Are data available for detailed analysis? YES Perform heat strain (physiological) Detailed analysis monitoring

107. http://www.slideshare.net/mikeslater mike@diamondenv.co.uk http://diamondenv.wordpress.com Twitter: @diamondenv Mike Slater

108. Mike Slater, Diamond Environmental Ltd. (mike@diamondenv.co.uk) This presentation is distributed under the Creative Commons Attribution-NonCommercial-ShareAlike UK:International Licence

TLVs for heat stress

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TLVs for heat stress