Table 1
Symptoms of heat illness.
| Symptoms of Heat Illness | Heat Illness |
|---|---|
| Painful spasm of muscle in the arms, legs or abdomen | Heat Cramps |
| Headache, nausea, vomiting, weakness and fatigue | Heat Exhaustion |
| Dizziness or light-headedness, Moist and pale skin | |
| Rapid heart rate and breathing, irritability | |
| High body temperature, hot and dry skin, | Heat Stroke |
| Confusion or disorientation, loss of consciousness | |
| Seizures, irrational behavior |
Table 2
Demographic and anthropogenic characteristics of study participants.
| Variables | Frequency | Percent (%) |
|---|---|---|
| Gender | ||
| Male | 55 | 91.7 |
| Female | 5 | 8.3 |
| Age Group (Years) | ||
| 20–29 | 31 | 51.7 |
| 30–39 | 25 | 41.7 |
| 40–50 | 4 | 6.7 |
| BMI Group (kg/m2) | ||
| Underweight < 18.5 | 1 | 1.7 |
| Normal 18.5–24.9 | 25 | 41.7 |
| Overweight 25–29.5 | 31 | 51.7 |
| Obesity > 30 | 3 | 5.0 |
| Employment Status | ||
| Main Operator | 43 | 71.7 |
| Contractor | 17 | 28.3 |
Table 3
Demographic and anthropogenic characteristics of study participants working in underground and open cut.
| Variables | Underground (n = 37) | Open Cut (n = 23) | P-Value |
|---|---|---|---|
| Age (years) | 30.11 ± 6.41 | 30.52 ± 5.19 | 0.512 |
| Height (m) | 171.41 ± 8.51 | 173.83 ± 5.81 | 0.459 |
| Body Mass (kg) | 74.2 ± 6.7 | 76.1 ± 8.3 | 0.058 |
| BMI (kg/m2) | 25.4 ± 2.8 | 25.1 ± 2.2 | 0.526 |
Table 4
Reported heat illness symptoms among open cut and underground miners.
| Heat illness symptoms | Open cut (n = 23) | Underground (n = 37) | Chi-Square | p-value | Total (n = 60) |
|---|---|---|---|---|---|
| Muscle cramp | 7 (30.4) | 15 (40.5) | 0.624 | 0.430 | 22 (36.7) |
| Headache | 15 (65.2) | 25 (65.6) | 0.035 | 0.851 | 40 (66.7) |
| Nausea | 2 (8.7) | 0 | – | – | 2 (3.3) |
| Vomiting | 2 (8.7) | 0 | – | – | 2 (3.3) |
| Weakness | 13 (56.7) | 22 (59.5) | 0.50 | 0.822 | 35 (58.3) |
| Fatigue | 15 (65.2) | 24 (64.9) | 0.001 | 0.978 | 39 (65.0) |
| Dizziness | 2 (8.7) | 2 (5.4) | – | – | 4 (6.7) |
| Moist skin | 19 (82.6) | 34 (91.9) | 1.186 | 0.276 | 53 (88.3) |
| Irritability | 7 (30.4) | 13 (35.1) | 0.141 | 0.707 | 20 (33.3) |
| Hot and dry skin | 21 (91.3) | 33 (89.2) | 0.071 | 0.791 | 54 (90.0) |
| High body temperature | 21 (91.3) | 36 (97.3) | 1.072 | 0.300 | 57 (95.0) |
| Confusion | 6 (26.1) | 13 (35.1) | 1.212 | 0.271 | 19 (31.7) |
| Irrational behavior | 8 (38.4) | 7 (18.9) | 1.904 | 0.168 | 15 (25.0) |
| Low coordination | 1 (4.3) | 1 (2.7) | – | – | 2 (3.3) |
| Loss of consciousness | 1 (4.3) | 1 (2.7) | – | – | 2 (3.3) |
Table 5
Heat illness by potential study variables.
| Study Variables | Heat Illness | Chi-Square | p-value | |
|---|---|---|---|---|
| Minor Heat Illness | Moderate Heat Illness | |||
| Mining site | ||||
| Underground | 8 (21.6) | 29 (78.4) | 0.588 | 0.443 |
| Open cut | 7 (30.4) | 16 (69.6) | ||
| Job category | ||||
| Jumbo offsiders | 8 (25.0) | 24 (75.0) | 0.055 | 0.973 |
| Charge up/service crew | 5 (26.3) | 14 (73.7) | ||
| Quality controller | 2 (22.2) | 7 (77.8) | ||
| Employee’s status | ||||
| Operators’ Employee | 8 (18.6) | 35 (81.4) | 3.311 | 0.069 |
| Contractors’ Employee | 7 (41.2) | 10 (58.8) | ||
Table 6
WBGT index and physiological measures by mining sites.
| Parameters (n = 60) | Underground | Open cut | p- value | |
|---|---|---|---|---|
| (n = 37) | (n = 23) | |||
| Average wet-bulb globe temperature (°C) | 27.09 ± 1.51 | 28.92 ± 1.87 | 0.000 | * |
| Average dry-bulb temperature (°C) | 30.1 ± 1.4 | 31.9 ± 2.1 | 0.000 | * |
| Average relative humidity (%) | 69.1 ± 7.8 | 40.72 ± 9 | 0.000 | * |
| Average air velocity (m/s) | 0.75 ± 0.25 | 1.74 ± 0.39 | 0.000 | * |
| Core body temperature before (°C) | 35.9 ± 1.7 | 36.5 ± 0.5 | 0.151 | |
| Core body temperature after (°C) | 37.3 ± 0.5 | 38.4 ± 0.5 | 0.000 | * |
| Rise in core body temperature (°C) | 1.1 ± 0.6 | 1.9 ± 0.8 | 0.000 | * |
| Pulse rate before (beat/minute) | 70.9 ± 14.6 | 81.35 ± 12.4 | 0.007 | * |
| Pulse rate after (beat/minute) | 94.7 ± 19.5 | 109.65 ± 15.9 | 0.003 | * |
| Rise in pulse rate (beat/minute) | 23.2 ± 15.3 | 28.30 ± 17.0 | 0.241 | |
| Systolic blood pressure before (mmHg) | 128.4 ± 11.7 | 129.3 ± 11.5 | 0.773 | |
| Systolic blood pressure after (mmHg) | 144.2 ± 13.8 | 149 ± 12.9 | 0.195 | |
| Rise in systolic blood pressure (mmHg) | 15.8 ± 8.4 | 19.7 ± 6 | 0.066 | |
[i] *Significant at p < 0.05, Data summarizes mean ± SD.
Table 7
Physiological measures by job category.
| Factors | Jumbo offsiders/offsiders (n = 32) | Charge up/service crew (n = 19) | Quality controller (n = 9) | F | p-value | |
|---|---|---|---|---|---|---|
| Core body temperature before (°C) | 36.25 ± 0.5 | 35.8 ± 2.3 | 36.68 ± 0.69 | 1.283 | 0.285 | |
| Core body temperature after (°C) | 37.8 ± 0.7 | 37.34 ± 0.6 | 38.5 ± 0.5 | 9.510 | 0.000 | * |
| Rise in core body temperature (°C) | 1.63 ± 0.8 | 1.01 ± 0.5 | 1.81 ± 0.7 | 5.284 | 0.008 | * |
| Pulse rate before (beats/min) | 75.84 ± 14.4 | 66.78 ± 10.5 | 89 ± 11.7 | 9.119 | 0.000 | * |
| Pulse rate after (beats/min) | 104.18 ± 17.3 | 89.94 ± 20.1 | 109.5 ± 17.6 | 4.884 | 0.011 | * |
| Rise in pulse rate (beats/min) | 27.71 ± 14.6 | 23.15 ± 19.2 | 20.55 ± 13.6 | 0.920 | 0.404 | |
| Systolic blood pressure before (mmHg) | 127.34 ± 10.2 | 126.57 ± 13.3 | 138.3 ± 7.9 | 4.004 | 0.024 | * |
| Systolic blood pressure after (mmHg) | 143.4 ± 10.64 | 144.57 ± 16.04 | 158.88 ± 11.4 | 5.435 | 0.007 | * |
| Rise in systolic blood pressure (mmHg) | 16.06 ± 6.3 | 18 ± 9.9 | 20.55 ± 7.1 | 1.271 | 0.288 | |
Table 8
Association between environmental factors and physiological change.
| Environmental factors | Rise in core body temperature | Rise in pulse rate | Rise in systolic blood pressure |
|---|---|---|---|
| Average dry-bulb temp | 0.503* (p = 0.00) | 0.006 (p = 0.962) | 0.096 (p = 0.466) |
| Average WBGT | 0.410* (p = 0.001) | –0.051 (p = 0.701) | 0.033 (p = 0.801) |
Figure 1
Correlation between WBGT and rise in core body temperature.
Figure 2
Correlation between dry-bulb temperature and rise in core body temperature.
Table 9
Hydration practices among mine workers and heat illness.
| Hydration characteristics | Frequency (%) | Chi-square | p-value | |
|---|---|---|---|---|
| Accessibility to free drinking water | ||||
| Yes | 41 (68.3) | 8.067 | 0.005 | * |
| No | 19 (31.7) | |||
| Fluid intake before commencing work | ||||
| None | 25 (41.7) | 36.33 | 0.000 | * |
| <250 ml | 21 (35.0) | |||
| 250–500 mls | 8 (13.3) | |||
| 500–1,000 mls | 5 (8.3) | |||
| >1,000 mls | 1 (1.7) | |||
| Fluid consumption during shift | ||||
| 1,500 mls | 2 (3.3) | 26.800 | 0.000 | * |
| 3,000 mls | 34 (56.7) | |||
| >3,000 mls | 24 (40.0) | |||
| Fluid intake before commencing work | Minor Heat illness | Moderate heat illness | Total | |
| None | 7 (28.0) | 18 (72.0) | 25 (41.7) | |
| <250 ml | 6 (28.6) | 15 (71.4) | 21 (35.0) | |
| 250–500 mls | 0 | 8 (1000 | 8 (13) | |
| 500–1,000 mls | 2 (40) | 3 (60) | 5 (8.3) | |
| >1000mls | 0 | 1 (1000) | 1 (1.7) | |