# Climate-Related Heat Stress and Psychological Outcomes in Self-Employed Delivery Workers: Evidence from Brasília, Brazil

## TL;DR

This study finds that rising temperatures worsen stress, fatigue, and mood in self-employed delivery workers in Brasília, Brazil.

## Contribution

The study provides empirical evidence linking daily heat exposure to psychological strain in a platform-based outdoor workforce.

## Key findings

- Each 1°C increase in temperature was associated with higher stress, fatigue, and worse mood among delivery workers.
- Relative humidity had small but reliable effects on stress, fatigue, and mood despite strong collinearity with temperature.
- Heat exposure impacts psychological outcomes in a precarious workforce, suggesting policy interventions could help mitigate risks.

## Abstract

This study examines whether daily heat exposure worsens psychological well-being among self-employed motorcycle delivery workers in Brasília, Brazil. Using ecological momentary assessment over 15 consecutive days in August 2025, 45 workers were recruited and 30 (66.7%) completed twice-daily mobile prompts (12:00 and 18:00) rating stress, fatigue, mood, and perceived heat (1–5 scales) and reporting kilometers traveled. Environmental data (temperature, relative humidity, barometric pressure) were paired from the INMET Brasília station. Linear regressions with cluster-robust standard errors by participant tested associations. Higher temperature was consistently related to greater strain: each +1 °C was associated with higher stress (β = 0.196, 95% CI 0.179–0.213), higher fatigue (β = 0.289, 95% CI 0.284–0.295), and worse mood (β = 0.149, 95% CI 0.130–0.168). Adding relative humidity yielded small but reliable partial effects (lower stress and better mood, yet higher fatigue) amid strong dry-season collinearity between temperature and humidity. The findings indicate that even modest day-to-day warming corresponds to measurable deterioration in psychological outcomes in a precarious, outdoor, platform-mediated workforce. Policies that expand hydration and shaded rest access, integrate heat indices into alerts, and adapt platform scheduling to reduce peak-heat exposure may mitigate risk.