Table 1.

Summary of Study Groups, Procedures, and Measures

Group	Procedure	Definition
Cross Sectional (CS) Group	Definition	Larger sample of workers (n=148) who completed a heat-related illness (HRI) survey
	HRI Symptom Survey	A heat-related illness (HRI) symptom survey derived from the PNASH during the first week of farm work of crop production tasks.
	Medical Record Audit	A post-season medical record audit conducted to determine individuals who sought medical attention for Heat-Related Illness symptoms.
Intensive Surveillance (IS) Group	Definition	A smaller sample of workers (n=20) focused who fitted with a multi-parameter monitoring wearable sensor that measured a physiological response to the effort of farm work tasks.
	Physiological Response	Measured heart rate, breathing rate/chest excursion, skin temperature and kilocalories per hour. Baseline blood pressure, serum glucose and serum osmolarity was taken before field work commenced.
	Field Trial	A period of 2–4 hours starting after 12PM. The length of the field trial was determined by the farm crew leader based on their own perception of safety. Field trials were measured in minutes. There were n=57 field trials complete by participants in the IS group. These field trials are repeat measures but vary due to random climate conditions and length of work session (as determined by their employer/crew leader).
	Wet Bulb Globe Temperature (WGBT)	Climate condition measure that takes into account natural elements of the climate conditions. WBGT = 0.7Tw + 0.2Tg + 0.1Td where Tw = Natural we-bulb temp (humidity indicator), Tg = Globe thermometer temp (solar radiation), and Td = Dry-bulb temp (normal air temp). The WBGT considers wind, barometric pressure, and relative humidity. Research team measured climate conditions were not communicated to crew leaders, it was up to their employer to determine unsafe heat and humidity conditions.
	Physiological intensity (PI)	The physiological intensity score is a summary computation of heart rate and the intensity of the work performed based on a scale of 0–5. This measure were taken continuously during field trials.
	Core Body Temperature	A computed estimate of core body temperature based on the skin sensors. This measure were taken continuously during field trials.
	HRI Symptom Survey	A small piece of paper with a picture-based HRI symptoms with Spanish &English word descriptions were given at the end of each field trial. These HRI adopted from the PNASH survey.

Note. HRI= heat-related illness; PNASH = Pacific Northwest Agricultural Safety and Health Center; WBGT= wet bulb globe temperature