6.4 Heat Stress versus Pesticide Poisoning

National Core puts heat stress in the same hazards-and-first-aid chapter as pesticide poisoning because the two are easy to confuse and easy to stack. 40 CFR 171.103(c)(2)(v) and (vi) already require precautions that protect the applicator and proper use of protective clothing; those same layers of chemical-resistant gear that cut dermal dose also trap heat and block evaporative cooling. Oklahoma makes the overlap seasonal and occupational. Wheat harvest in western and northern counties often runs through late-spring and early-summer stretches of 90°F-plus days, with night work under still, humid air. Summer turf crews walk radiated asphalt and sand-based greens in July. Category 6 ROW work sits on blacktop and rock with no shade. Category 7A restaurant accounts look "indoor," yet dish rooms, bakeries, and closed dining rooms after hours can exceed outdoor temperatures. Grain-bin work combines confined heat, dust, and, when fumigants are in play, an inhalation poison on top of the heat load. An enclosed tractor or spray cab with working air conditioning is a different microclimate than an open ATV on a county road right-of-way with a backpack or hand gun.

Heat exhaustion versus heat stroke

Heat exhaustion is the body's response to heavy loss of water and salt, usually through sweating. OSHA lists fatigue, irritability, thirst, nausea or vomiting, dizziness, heavy sweating, and an elevated temperature or fast heart rate. The person may still be talking and walking. This is already a stop-work event: move to shade or a cooled cab, loosen or remove extra layers that are not required for a chemical emergency, provide cool water, and get medical evaluation if symptoms do not clear quickly. NIOSH and OSHA both warn that heat illness can worsen in minutes.

Heat stroke is failure of temperature control. NIOSH describes body temperature that can climb to about 106°F within 10 to 15 minutes, with a real chance of permanent injury or death without emergency care. National Core notes that more than 10 percent of severe heat-stress victims die, including young healthy adults, and that some remain heat-sensitive for months. It is a medical emergency. OSHA's current first-aid teaching is blunt: confusion, slurred speech, or unconsciousness means call 911 immediately and cool the worker with ice or cold water until help arrives. Skin signs vary. Classic textbook heat stroke was "hot, dry, red skin and no sweat." OSHA's table now lists heavy sweating or hot, dry skin. National Core still mentions progression from heavy sweating to a lack of sweating as the body loses control, and an older Core review item treated lack of sweat as a heat-stroke clue. Do not wait for a dry armpit before you call. When in doubt, cool the worker and call 911. Stay with the person. Move them to shade, remove outer clothing, wet the skin, and circulate air. Ice packs at the neck, armpits, and groin speed cooling. Do not hand a confused person a bottle and send them back to the boom.

Acclimatization matters. New hires and anyone returning after time away should build heat exposure over about a week, not "tough it out" on the first 100°F turf day. OSHA/NIOSH hydration teaching for moderate work in the heat is on the order of a cup of water every 15 to 20 minutes, not a single chug at lunch. Urine should stay pale. Extra salt tablets are not a field protocol unless a clinician directs them; regular meals usually replace electrolytes. Pregnancy, some blood-pressure medicines, antihistamines, older age, and a prior heat illness raise risk. Those are medical facts, not excuses to skip labeled pesticide PPE; they are reasons to redesign the job with more breaks, cooling, and staffing.

Why PPE, cabs, kitchens, and bins change the heat equation

National Core states that PPE worn during handling or early-entry work may increase heat-stress risk because it restricts sweat evaporation. A chemical-resistant coverall, gloves, boots, and respirator on a Category 1 mixer at a wheat nurse tank in June is a different heat engine than a long-sleeve shirt on a CAUTION granular spreader. Ice-pack vests and cooling bandannas are recognized Core-era tools under PPE; they do not cancel the need for rest cycles. An enclosed cab with intact filters and air conditioning can lower both drift exposure and heat load. It does not help the loader standing in the sun, the technician who steps out to clear a clogged nozzle, or the ATV driver with no cab. A 7A crew treating a closed restaurant in August may have no breeze at all; indoor heat illness is still heat illness. Grain bins can feel like ovens; adding a fumigant does not make the heat safer.

Stop work when someone is ill. A harvest schedule, a golf-tournament deadline, or a restaurant opening time is not an antidote. 40 CFR 171.103(c)(2)(v) is about preventing injury to applicators and others; pushing a stumbling coworker back onto an ATV fails that competency whether the cause is heat, an OP, or both.

Overlap, and how not to guess wrong

Shared findings include sweating, nausea, headache, dizziness, weakness, confusion, and collapse. That list appears in heat exhaustion, in some heat-stroke cases, and in mild-to-moderate cholinesterase poisoning. It also appears in dehydration after a long ROW day with no chemical on the skin. You will not settle the differential diagnosis from a single symptom in a pickup.

Use the job history and a few discriminating signs, then treat the emergencies in parallel.

Constricted (pinpoint) pupils are not a heat-stroke finding. National Core uses that contrast in review questions. If the crew just applied an organophosphate or carbamate, treat nausea, sweating, and confusion as possible poisoning until proven otherwise. Remove contaminated clothing, wash, call 1-800-222-1222 and 911, and give clinicians the label. Cooling a heat-stroke patient is still correct if the person is altered in July; decontamination is still correct if product is on the skin. You can do both. You cannot safely "assume it is just heat" to save the time a shower would take.

Pyrethroid paresthesia can feel like sunburn or tingling and is not heat stroke. A 7A pyrethroid job in a hot kitchen can still produce heat exhaustion in the same hour as skin tingling; treat heat as heat and skin exposure as skin exposure. Fumigant inhalation in a bin can look like collapse from heat syncope (fainting on standing). If a fumigant was used, it is an inhalation rescue problem with PPE, not a "get some air and walk it off" problem.

Putting an Oklahoma day together

Plan the day as if both hazards are real. Check the label PPE, then check the heat: water in the truck, shade or a cooled cab, rest rotation, and a buddy who will say stop. On wheat harvest and ROW, watch open-station equipment. On turf, watch dark clothing and midday radiant heat. On 7A restaurant work, watch closed, unventilated rooms. In bins, watch confined heat plus whatever gas is on the label. If someone becomes confused, cool, call, and decontaminate. If a cholinesterase inhibitor was in the tank, say that word out loud to EMS. Independent OpenExamPrep study material cannot replace the label or the Poison Center, but it can keep you from treating a medical emergency as a character test about finishing the field.