Occupational Heat Stress on Workers' Productivity
Condition: Risk of Heat Stress
MeSH terms: Heat Stress Disorders
Study type: Interventional

Summary: 
      Workplace heat exposure affects billions of people during their everyday work activities.
      Occupational heat stress impairs workers' health and capacity to perform manual labour.
      Therefore, the aim of this study was to observe the heat strain experienced by workers in
      occupational settings and test different strategies to mitigate it during actual work shifts
      in agriculture, manufacture, tourism, construction, and other services.
    

Detailed description: 
      The participants followed the study protocol which included, one work shift of sham
      measurements, one work shift business as usual and four (4) different scenarios
      (interventions) on different work shifts. Apart from the sham measurements the rest of the
      scenarios were tested in a random order for different participants.

        1. Work/ rest scenario: The participants were asked to take planned breaks in the shade
           during their work shift. The amount of breaks taken ranged between 3 and 10 minutes
           every hour depending on the current work duties of the employees.

        2. Hydration scenario: The participants were advised (not forced) to drink minimum of 750
           ml of water or ice - slushies, every hour during their work shift.

        3. Clothing scenario: The participants were randomly provided with different types of
           clothing, i.e. white breathable coveralls, ventilated garments and breathable uniform
           with water submerging parts, to wear during their work shift.

        4. Assisted labor: The participants in agriculture, that were carrying heavy weights were
           provided with "e-carts" (automated carrying vehicles), during their work shift.

      Baseline data [self-reported age; body stature (Seca 213; seca GmbH & Co. KG; Hamburg,
      Germany) and body mass (BC1000, Tanita corporation, Tokyo, Japan)] were collected one day
      prior to the measurements. Medical history of all the participants was recorded. During the
      field study, continuous heart rate, core temperature and mean skin temperature data were
      collected using wireless heart rate monitors (Polar Team2. Polar Electro Oy, Kempele,
      Finland), telemetric capsules (BodyCap, Caen, France), and wireless thermistors (iButtons
      type DS1921H, Maxim/Dallas Semiconductor Corp., USA), respectively. Skin temperature data
      were collected from four sites (chest, arm, thigh, and leg) and were expressed as mean skin
      temperature according to the formula of Ramanathan (Tsk = [0.3(chest + arm) + 0.2(thigh +
      leg)]). Furthermore, continuous environmental data [air temperature (°C), globe temperature
      (°C), relative humidity (%), and air velocity (m/s)] were collected using a portable weather
      station (Kestrel 5400FW, Nielsen-Kellerman, Pennsylvania, USA). Urine samples were collected
      at the start and the end of the work shift to evaluate the hydration status of each worker.
      Urine specific gravity was assessed for each urine sample using a refractometer (PAL-10S,
      ATAGO CO., LTD., Fukaya, Saitama Prefecture, Japan) and was classified as either hydrated (<
      1.020) or dehydrated (≥ 1.020). In addition, urine colour was assessed using a urine color
      scale. Questionnaires were used to assess workers' perception on exertion (Borg scale),
      thermal comfort/sensation, humidity comfort/sensation, radiation comfort/sensation, wind
      speed comfort/sensation, skin wetness, sleepiness, physical demands of the workload. The Heat
      Strain Score Index (HSSI) was used to assess the perceived heat strain of the workers.

      Video cameras installed in close proximity (about 40m) to the workers were used to assessed
      workers labour effort. Video recordings were analyzed on a second by second basis using
      time-motion analysis method. Importantly, when video cameras were not feasible to be
      installed real-time task analysis was used to examine workers capacity for manual labour. For
      that reason, an android-based application (FAME_TASK App) was used to record the tasks of the
      workers on a second by second basis. The App was continuously monitoring the work time spent
      on irregular work breaks (unplanned breaks), the duration of uninterrupted work and the time
      spent as lunch time or other breaks provided by management (planned breaks). The unplanned
      break was divided into two categories: the breaks during which the workers decided to rest in
      the shade (unplanned break under the shade) and the breaks during which the workers chose to
      stay under the sun (unplanned break under the sun). Also, the uninterrupted work was divided
      into nine categories: work in an outdoor environment with a low metabolic rate; work in an
      outdoor environment with a moderate metabolic rate; work in an outdoor environment with a
      high metabolic rate; work in a mixed (outdoor and indoor) environment with a low metabolic
      rate; work in a mixed (outdoor and indoor) environment with a moderate metabolic rate; work
      in a mixed (outdoor and indoor) environment with a high metabolic rate; work in an indoor
      environment with a low metabolic rate; work in an indoor environment with a moderate
      metabolic rate; work in an indoor environment with a high metabolic rate. The labor effort
      (i.e., low / moderate / high metabolic rate) was defined according to the ISO 8996:1994 as
      low, moderate and high metabolic rate. Based on these definitions, the recorded tasks were
      fourteen. During the work-shift, a researcher was following each worker, monitoring them with
      the FAME_TASK App, until they end of their work shift.
    

Intervention name(s): Work/ rest scenario; Hydration scenario; Clothing scenario; "E-carts" scenario; Business as usual scenario; Sham evaluation
Intervention type(s): Other; Other; Other; Other; Other; Other
Intervention description(s): For every hour of work, the participants were asked to take 3-10 minutes break in the shade.; Participants were asked to consume at least 750ml of water or ice-slushies for every hour of work; Participants were asked to wear different types of clothing during the work shift i.e. ventilated garments, white breathable coveralls, clothing with water submerged parts; Participants that were involved in manual labor by carrying heavy weights were provided with "e-carts" (automated carrying vehicles); No interference with the usual work day of the participants; Participants were monitored during a usual day of work shift while sham measurements were recorded in order for them to get familiarized with the study environment
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Single (Participant)
Primary purpose: Prevention
Keywords: heat stress; heat strain; productivity; labor; occupation; work; thermal