Occupational HazardsOccupational Hazards

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Heat StressImproving safety in the Arabian Gulf oil and gas industry

By Oliver F. McDonald, Nigel J. Shanks and Laurent Fragu

WITH INCREASED OILAND GAS DEVELOPMENTin very hot areas of the world, heat-related disordersand heat stress prevention require practical proce-dures to protect workers. The situation is so criticalthat the State of Qatar has banned midday workinghours for certain employees during the hottest timesof the year. The program described in this article wasused to index the severity of work situations and pro-vide simple heat-stress-preventive work practices to avery large population of workers. The result was areduction of heat-stress-related medical treatmentsfrom 0.164 incidents/200,000 workhours to 0.012within 3 years.

The Call for CoolDespite exposure to a wide range of environmen-

tal temperatures, the human body maintains a coretemperature of 98.6 °F (37 °C) with a narrow rangeof normal variation. Those who work under severeenvironmental conditions may suffer from seriousphysical injury due to the effects of extreme elevationor depression of body temperature. Hyperthermia, inparticular, has been associated with occupationaldeaths (Sherman, Copes & Stewart, 1989). Extremesof environmental temperature may be constant andpredictable, such as in a foundry or undergroundmine, or can vary with the time of year in outdooroccupations, such as farming or construction.

Heat stress disorders span a spectrum fromminor heat illness to heat exhaustion and heat stroke(Hubbard, 1990). Heat stroke is a medical emergencythat results from complete loss of thermoregulatorycontrol. As the ambient temperature climbs higherthan 95 °F (35 °C), virtually all heat loss is accom-plished by sweating. As the ambient relative humid-ity exceeds 75%, the rate of evaporation decreasesdrastically and sweating becomes an ineffectivemeans of dissipating heat (Urbano-Brown, Prouix &Schwartz, 1999). Without effective heat dissipation,body temperature rises, potentially leading to heat-related disorders. Organ damage becomes evidentas tissue temperatures approach 107 °F (41.7 °C)(Harnett, Pruitt & Sias, 1983). Heat, humidity andlack of air movement are all conducive to heat stress.

Preexisting dehydration has serious deleteriouseffects and limits the potential cardiovascularresponse to the increased circulatory demands ofheat stress (Hubbard, 1990; Gisolfi & Wenger, 1984).

Water loss as a result of dehydration in hot workingenvironments is an issue that needs to be addressedsince it is associated with the development of bothheat exhaustion and heat stroke (Knochel, 1974).

The ConditionsTo effectively provide heat stress protection for

workers, supervisors need a real-time heat conditionmonitoring system. The heat index was chosen assuch a direct reading indicator of thermal comfort; it isbased on measurements of dry bulb air temperatureand relative humidity as used by the U.S. NationalOceanic and Atmospheric Administration (NOAA).Other parameters examined include the globe tem-perature, the wet bulb temperature, wind speed anddirection. The data presented in this article were gath-ered at a liquefied natural gas (LNG) facility in Qatar.

While the heat index or apparent temperature(Steadman, 1979) is a first-order indicator of thermalcomfort, it does not include the effect of convectiveor radiant heat exchange and does not consider themetabolic heat generation rate, air velocity, clothingor the nature of work (Bingham, Cohrssen & Powell,2001). Any of these factors can significantly alter theconditions for the worker. For example, clothingalters the rate of heat exchange between the skin andambient air (Ramsey & Bernard, 2000).

The heat index can be obtained by directly meas-uring the dry bulb temperature and the relativehumidity (using a natural wet bulb thermometer)and reading the corresponding heat index from achart like that shown in Figure 1 (p. 32), which wasadapted from NOAA’s existing heat index chart.Alternatively, heat stress monitors placed in fullshade in the workplace provided a direct reading ofthe heat index.

Oliver F. McDonald, CSP, CIH, is an industrial hygienist with RasGas Co. Ltd. inQatar. He previously was an industrial hygiene supervisor with Dow Chemical inFreeport, TX, and a consultant with URS Corp. He is a professional internationalmember of ASSE.

Nigel J. Shanks, M.D., Ph.D., M.B.A., is chief medical officer with RasGas Co.Ltd. Prior to this, he was chair of the accident and emergency department withthe Ministry of Health in United Arab Emirates. Shanks is a member of theAmerican College of Occupational and Environmental Medicine.

Laurent Fragu, M.S., is an environmental engineer with URS Qatar LLC. As aconsultant, he performs studies in the field of environmental assessment, airquality and industrial hygiene.

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Abstract: As oil andgas developmentincreases in theMiddle East, heat-related disorders andheat stress preventionare key concerns. Thisarticle examines theresults of the heatstress prevention pro-gram implementedby one company inQatar. The programproved to reduceheat stress injuries bymore than a factorof 10 over 3 years.

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which corresponded to the type of activities per-formed by a significant proportion of staff, includingconstruction workers involved in several majorexpansion projects who were the primary concernfor exposure to heat stress.

•Acclimatization to heat was assumed.Under these conditions, theACGIH screening cri-

teria for 25% work, 75% rest was exceeded and addi-tional personal evaluation of the task would havebeen required. Since it was anticipated that thesewould be the prevailing conditions for the months ofJuly and August in Qatar and the required personalmonitoring was not practical on a large scale, otherindexes were considered for use. In an effort to pro-vide flexibility and ease of measurement the heatstress index was selected as the monitoring criteria.

Specifically, the historical air temperature observedduring the month of August for the period of 1962 to2003 in Qatar was 95 °F (35 °C) and 118.4 °F (48 °C) forthe average and average maximum (CAA). These val-ues were obtained by averaging the reported dailyaverage and high temperatures, respectively. Theaverage and average maximum relative humiditywere 57% and 80%, respectively, calculated using asimilar methodology for the same timeframe. If noteffectively controlled, such conditions have led toheat-related disorders among workers (AIHA, 1975).

Data collected during the survey provided severalinteresting observations that were useful to defininginteractions of heat stress parameters; identifying keypatterns of heat stress conditions; and describing dayand night extreme heat conditions. Specifically, theconditions observed during August 2006 were typicaland resulted from the combined effect of high relativehumidity brought in by the east wind and elevated airtemperature. A total of 660 hours of monitoring datawas collected using heat stress monitors that recordeddry bulb temperature, natural wet bulb temperature,relative humidity, globe temperature and heat index at1-minute intervals. A nearby monitoring station(RLIC, 2006) recorded the wind conditions. The effectof providing shade under high relative humidity wasevaluated by comparing data from shaded and directsunlight heat stress monitor locations.

Daily PatternsFor the monitoring period (Aug. 6 to Sept. 18), the

daily averages of dry bulb temperature and relativehumidity were 94.5 °F (34.7 ºC) and 61%, respective-ly, corresponding to a heat index of 45, obtained asthe average of all the daily values used to createFigure 2. The average heat index parameters areillustrated throughout a 1-day cycle in Figure 2. Theparameters shown were obtained by averagingreadings for the corresponding 3-hour portion of theday over the monitoring period. Figure 3 shows asample daily pattern observed in September 2006.

Aheat index level of 54 was selected as the point atwhich all work should be stopped, as it is associatedwith extreme danger and potential heat stroke in theheat index chart (Figure 1). In addition, a heat indexlevel of 50 was defined as the point at which all ele-

Among the heat stress indexes that have beenproposed (Bingham et a., 2001), the wet bulb globetemperature (WBGT) is the current index supportedby the American Conference of GovernmentalIndustrial Hygienists (ACGIH, 2006). The ACGIHevaluation scheme was assessed to determine itsapplicability under the work conditions in Qatar.The normal daytime conditions in Qatar during theperiod of monitoring were a wet bulb temperatureof 82.4 °F (28 °C) and a globe temperature of 104 °F(40 °C) taken in the shade. These conditions corre-spond to a calculated WBGT value without directexposure to sun of 89 °F (31.6 °C). In addition:

•Clothing was assumed to allow air movement.No WBGT adjustment was made for clothing type.

•The heavy activities category was selected,

Figure 1Figure 1

Heat Stress Chart

Note. Adapted from U.S. NOAANational Weather Service Heat Index.

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direction in Qatar (CAA). Figure 4 (p. 34) shows theprevailing wind in Qatar throughout the year whileFigure 5 (p. 35) shows prevailing winds at Ras LaffanIndustrial City during August 2006.

While the prevailing wind in Qatar originated fromthe northwest desert areas, the prevailing wind forAugust originated from the east. This wind patternaccounted for elevated relative humidity blowing infrom the warm Arabian Gulf waters. Therefore, theextreme heat stress conditions resulted from the com-bined effect of elevated relative humidity driven bythe east wind and elevated air temperature.

vated, aboveground work wasstopped. This level is at thehigher end of the “danger” cate-gory (NOAA). This action levelwas established to reflect theincreased difficulty associatedwith elevated work, due to iso-lation and the difficulty ofcommunication and emergencyresponse. This practice is similarto that used by other companiesin the area. Approximately 10%of the heat index values exceed-ed 50 and 0.2% exceeded 54.Although the hottest time of theday was between 9:00 a.m. and10:00 a.m., the most dangerouswas between 11:00 a.m. and 2:00p.m., when the maximum heatindex occurred. The peak heatindex was observed at approxi-mately noon.

Excursions above key heatindex values of 50 and 54 wereseparated into night and dayperiods in order to check thegenerally held notion that it issafer to work at night from theviewpoint of heat stress risk(Table 1, p. 34).

This examination shows thatthe 50 and 54 thresholds wereexceeded 13.2% and 0.3% ofdaylight hours and 6.4% and0.1% of the nighttime hours.While the action point levelswere not exceeded as frequent-ly during nighttime hours,there was still a significant risk.The monitoring results indicat-ed that extreme heat conditionscan occur during the night,especially during times of ele-vated relative humidity.

For work planning purposes,approximately 20% of the work-ing hours were at a heat index of50 or above. Complete workstoppage at a heat index of 54 orabove (see Table 1) occurred lessthan 0.5% of the time.

A reduced number of instances above key heatindex levels were recorded during the last monitor-ing days, the beginning of September. Reduced airtemperature in September led to fewer readings pastthe 50 heat index value.

Wind DirectionWind speed and direction data from the Ras

Laffan Camp ambient air quality monitoring stationwere collected for the month of August 2006 andcompared against the typical annual wind speed and

Figure 2Figure 2

Average Heat Stress Parameters

Figure 3Figure 3

Sample Daily Heat StressMonitor Pattern

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•Low Relative Humidity(RH ≤ 35%): (∆GT)sun, shade~ 10 ºC

Therefore, under high rela-tive humidity conditions, pro-viding shade did not reduceheat stress as much as it didunder low relative humidityconditions. Additional con-trols, such as spot cooling andair movement, were neces-sary to mitigate the heat load.Combined with the examina-tion of wind direction and rel-ative humidity, it becameobvious that providing cool-ing, not just shade, wasimportant during periods

when the humidity was greater than 50%. Coolingmechanisms that rely on evaporation, such as evapo-rative bandanas, were also less effective under thesehigh relative humidity conditions. The GT data madeit clear that there was limited benefit in providingshaded areas under high relative humidity conditions.

Heat index monitoring was also conducted inspecific work situations, such as welding performedunder a tent, where the general heat index for thesite was not applicable. Although the environmentalconditions may have varied from those of the over-all site, the prescriptive response was still appropri-ate. Supervisors were able to use suitable work

practice controls once theyknew the heat index.

The Course ChosenAlthough considered as the

first option to reduce heat-relat-ed risk, application of engineer-ing controls (such as cooling,ventilation and shading) wasdifficult considering the scale ofthe activities performed—out-doors over an area of severalsquare miles. Additionally, inconstruction work, the environ-ment changes daily.

Therefore, engineering con-trols were applied mostly inrest areas and administrativecontrols were applied in workareas. PPE, such as umbrellasand evaporative bandanas,were used in the summer of2007. More than 25,000 ban-danas were distributed as wereinsulated water bottles. Similarconditions and practices maybe useful in projects such ashighway or bridge construc-tion during the hot months inother parts of the world.

In 2003, the company also

Shade vs. Direct SunlightIn addition to air temperature and relative humid-

ity, the influence of shade to reduce radiant heat loadwas also investigated using the globe temperature(GT). As a general pattern observed during the sur-vey, GT, representing the radiant heat exposure,decreased with rising relative humidity. As the rela-tive humidity increased, the amount of water in theair increased and the radiant heat absorbed or reflect-ed by water increased, thereby reducing the GT. Thefollowing relationship was observed while compar-ing GT under shade and direct sunlight conditions:

•High Relative Humidity (RH ≥ 50%):(∆GT)sun, shade ~ 2 to 4 ºC.

Excursions Above Key HI LevelsExcursions above HI levels Hours %

Day Total monitoring duration 349.2 100HI range HI ≥ 54a 1.1 0.3

50 ≤ HI < 54b 46.3 13.2Night Total monitoring duration 312 100

HI range HI ≥ 54 0.25 0.150 ≤ HI ≤ 53 19.95 6.4

Note. HI = heat index.aAll work stopped. bElevated work stopped.

Table 1Table 1

Figure 4Figure 4

Typical Wind Pattern in Qatar

Note. Doha International Airport.

Withincreased oil

and gasdevelopment

in very hotareas of the

world, heat-related

disordersand heat

stressprevention

requirepractical

proceduresto protectworkers.

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during nighttime demonstrated the need for heatstress controls during those hours as well.Accordingto the data on instances above key heat index values,there was a potential to stop elevated work during asignificant number of nighttime working hours dur-ing the month ofAugust. Daily work schedules wereadjusted when possible to anticipate and avoidexposure to the most extreme heat conditions.

The heat stress prevention procedure required thatrest shelters provided to construction or shutdownworkers be equipped with cool-down areas to achievea temperature differential of 7 to 15 °C. Shelters werecovered with sunscreen canopy allowing air flow withan open section below 1 meter in height.

The heat stress prevention program was alsodesigned to fit a multicultural working environment.Materials were available in English, Arabic, Hindi,Urdu, Nepali, Tamil and Thai. Additionally, training

introduced a heat stress prevention procedure basedon monitoring of the heat index as an indicator ofoverall heat stress conditions. Work practices to con-trol employee exposure to heat stress were imple-mented at that time. The heat stress preventionprocedure was developed based on available guide-lines from the oil and gas industry (E&PForum, 1998;OSHA, 1999). The heat index was selected for itspracticality, its adaptability to local conditions andthe ease of identifying adequate controls. When theheat index reached levels known to produce heat-related disorders, additional work practices wereimplemented (Table 2).

Other recommended practices incorporated intothe heat stress prevention procedures included workscheduling, acclimatization guidelines (Bernard,1995), self-evaluation, employee rotation, buddy sys-tem, shade and shielding, area cooling, clothing, ven-tilation and mechanical assistance.

Workers were given at least 1 week to acclimatizeto the environment; this allowed for maximum effi-ciency of heat control mechanisms for new workersor workers returning from leave or illness (Bernard,1995). Acclimatization was not facilitated by restrict-ing fluid intake; in fact, conscious attention to fluidintake was required to prevent dehydration.

Reliance on voluntary intake to maintain ade-quate fluid balance resulted in the development ofsignificant dehydration. It was important to providenumerous and easily accessible water stations andto mandate that workers drink water during restperiods. Water stations were placed inside or nearthe rest shelters. Color charts were posted in rest-rooms to indicate when additional fluid was neededbased on urine color (Figure 6, p. 36).

Current conditions were reported to supervisorsand workers through stationary and electronic infor-mation boards on the worksite; posted on the compa-ny intranet; and communicated through a messageservice alert system to cell phones. Heat stress com-munication materials were posted at key locations,including rest shelters. Small cards showing the datafrom Figure 1 and Table 2 were distributed. In addi-tion, flags that werecolor coded to theyellow, orange andred conditions inthe heat index wereflown above the con-struction project andcamps where theworkers lived, alert-ing them to theprevailing weatherconditions. This en-sured that heat stressinformation wasmore widely avail-able to those whoneeded it the most.

Elevated heat in-dex values recorded

Figure 5Figure 5

Wind Pattern in August

Note. Ras Laffan Industrial City, 2006.

Suggested Preventive Heat Stress Work PracticesWork:Rest period Water requirementsa

Heat index (minutes) Progressive controls

27-31 50:10 1 cup/20 min Continuous visual monitoring ofworkers in direct sun and heavy work

32-38 40:10 1 cup/20 min No working alone, self-paced39-49 30:10 1 cup/15 min Work under shade50-53 20:10 1 cup/10 min Elevated work stopped≥ 54 -- -- All work stopped

Note. As heat index increases, additional controls should be implemented as indicated.a1 cup ~ 1⁄4 L.

Table 2Table 2

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Results of the survey conducted during the mostextreme heat conditions in Qatar provided good indi-cations to adapt future working schedules based onheat conditions and to plan for future project execution.

Table 3 shows the program’s results. The data aresignificant because approximately 1 million work-hours were logged per week toward the end of thistime, including operations of LNG, gas treatmentonshore and offshore facilities, and construction activ-ities related to several expansion projects. The successof this program was recognized as a significant workpractice during a recent external audit.

Future efforts to reduce heat-related medicaltreatments will include monitoring heat conditionsduring the months of May, June and July and furtherverification of the work practices implemented. �

ReferencesAIHA. (1975). Heating and cooling for man in industry (2nd ed.).

Akron, OH: AIHA.American Conference of Governmental Industrial Hygien-

ists. (2006). Threshold limit values and biological exposure indices forchemical substances and physical agents. Cincinnati, OH: Author.

Bernard, T. (1995). Thermal stress: Fundamentals of industrialhygiene (4th ed.). Chicago: National Safety Council.

Bingham, E., Cohrssen, B. & Powell, C. (Eds.) (2001). Patty’sindustrial hygiene and toxicology. New York: John Wiley & Sons.

Civil Aviation Authority (CAA). Long-term means and ex-tremes of climatological elements 1962-2003. Doha, Qatar: Author,Doha International Airport Meteorology Department and ClimateSection.

E&P Forum. (1998). Health aspects of work in extreme climateswithin the E&P industry (Report No. 6.70/279). London: Author.

Gisolfi, C.V. & Wenger, C.B. (1984). Temperature regulationduring exercise: Old concepts, new ideas. Exercise Sport Science, 12,339-373.

Harnett, R.M., Pruitt, J.R. & Sias, F.R. (1983). A review of theliterature concerning resuscitation from hypothermia: Part 1—Theproblem and general approaches. Aviation Space EnvironmentalMedicine, 5, 425-434.

Hubbard, R.W. (1990). An introduction: The role of exercise inthe etiology of exertional heat stroke. Medical Science of SportsExercise, 22, 2-5.

Knochel, J.P. (1974). Environmental heat illness: An eclecticreview. Archives of Internal Medicine, 133, 841-863.

OSHA. (1999). Heat stress. In OSHA Technical Manual, SectionIII, Chapter 4. Washington, DC: Author.

Ramsey, J. & Bernard, T. (2000). Heat stress. In R. Harris (Ed.)Patty’s industrial hygiene and toxicology, Volume 2. New York: JohnWiley & Sons.

Ras Laffan Industrial City (RLIC). (2006). RLIC camp ambientair quality monitoring station, personal communication, Sept. 14,2006.

Shanks, N.J. & Papworth, G. (2001). Environmental factorsand heat stroke. Occupational Medicine, 51, 45-49.

Sherman, R., Copes, R. & Stewart, R.K. (1989). Occupationalhealth due to heat stroke: Report of two cases. Canadian MedicalAssociation Journal, 140, 105-107.

Steadman, R. (1979). The assessment of sultriness. Part I: Atemperature-humidity index based on human physiology andclothing science. Journal of Applied Meteorology, 18, 861-873.

U.S. National Oceanic and Atmospheric Administration(NOAA). NOAA’s weather service heat index. Retrieved June 23,2008, from http://www.nws.noaa.gov/om/heat/index.shtml.

Urbano-Brown, A., Prouix R.P. & Schwartz, G.R. (1999). Heatstress diseases in principles and practice of emergency medicine (4thed.). Philadelphia: Lea & Febiger.

AcknowledgmentsThe authors would like to thank Ellen McDonald, a member ofthe safety, health and environment group, occupational healthdepartment medical team, and Ras Laffan Industrial City.

was provided tonew and existingemployees and con-tractors to explainheat stress symp-toms, the heat indexsystem, the colorcoding and the con-trols implemented.The heat stress topicwas also covered invarious safety talksand in the companynewspaper.

ConclusionA previous study

established that thenumber of heat-related disorders inareas under extremeheat conditions was

best correlated with the combination of the dry airtemperature and the relative humidity (Shanks &Papworth, 2001). Although other indexes have beendeveloped to include other heat stress contributingfactors, such as metabolic factors, the main benefit ofusing the heat index was its ease of use.

Environmental and working conditions in theArabian Gulf make heat stress prevention a safety andhealth priority. The scale and intensity of oil and gasactivities in that part of the world require a simple,easy-to-apply program that can be used in manyworkplaces where a need exists to monitor and con-trol heat conditions. Monitoring parameters and asso-ciated work practices formed the core of the program,along with select engineering controls, training andother communication tools. Simple adaptation of thework practice guidelines allowed the selectedmethodology to be applied in other natural, economi-cal and cultural environments.

Prevention of the heat-related problems was facili-tated through real-time monitoring of the heat index.The reliance on the heat index system provided ade-quate and direct indication that further work controlswere needed without relying on arbitrary timing.

Figure 6Figure 6

Guide to Dehydration

Reduction of Heat-Stress IncidentsRatea Totalb Workhoursc

2003 0.164 25 31,000,0002004 0.044 7 32,000,0002005 0.010 2 40,000,0002006 0.012 3 52,000,000

Note. aBased on 200,000 hours of exposure. bTotal reported cases, excluding firstaids. cIncluding offshore and onshore operations.

Table 3Table 3

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