New Zealand’s summer sun is deceptive. UV levels here are among the highest in the world — up to 40% higher than comparable latitudes in Europe or North America — because of the thinner ozone layer over the Southern Hemisphere and New Zealand’s clean, unpolluted air. For tradies and outdoor workers spending long days on site, the risks go well beyond getting a bit red.
The Spectrum of Heat-Related Illness
Heat-related illness exists on a spectrum, and it can escalate faster than most workers expect:
- Heat cramps: Muscle spasms caused by electrolyte loss through sweat. Painful but manageable with rest, fluids, and electrolyte replacement.
- Heat exhaustion: Heavy sweating, weakness, cold or pale skin, a fast or weak pulse, nausea. Move the worker to a cool area, apply cool cloths, and provide fluids immediately.
- Heat stroke: Body temperature above 40°C, hot and red skin, fast and strong pulse, possible unconsciousness. This is a medical emergency requiring immediate ambulance call.
The shift from heat exhaustion to heat stroke can happen in minutes, particularly when a worker is already dehydrated or is wearing heavy PPE that prevents heat dissipation.
UV Exposure and Skin Cancer Risk
New Zealand has one of the highest rates of melanoma in the world. Outdoor workers accumulate sun exposure across a career in a way that significantly elevates their lifetime risk. The construction industry has a disproportionate burden of skin cancer cases because the workforce is predominantly male, predominantly outdoor, and — historically — has treated sun protection as optional.
The SunSmart message — Slip, Slop, Slap, Wrap — applies directly on site. Long-sleeved shirts, sunscreen (SPF 50+) reapplied every two hours, broad-brimmed hats, and UV-blocking eyewear are the baseline. Shade during lunch breaks is not a luxury; it’s a health measure.
Employer Obligations
Under the Health and Safety at Work Act 2015, employers must manage risks from heat and UV exposure as they would any other workplace hazard. This means assessing the risk (hours of outdoor work, UV index on the day, workload intensity), implementing controls, and providing adequate facilities including cool drinking water, shaded rest areas, and access to sunscreen.
Scheduling heavy work earlier in the morning and taking proper breaks during peak UV hours (10am to 4pm) is the most effective single control available. Acclimatisation for workers new to outdoor summer work — particularly those coming from indoor environments — takes 10-14 days and significantly reduces risk during that period.
Hydration Is Not Optional
Workers performing hard physical labour in summer heat can lose two or more litres of fluid per hour. By the time thirst kicks in, you’re already mildly dehydrated. Consistent fluid intake — at least 250ml every 20 minutes in hot conditions — prevents the performance decline and safety risk that come with dehydration.