Improving worker conditions in Brick kilns: A Randomized Controlled Trial in Bangladesh

Owners of kilns in the intervention arm will receive an integrated technical and work conditions training package (ZZK2.0+) which includes a refresher training on the proven Zigzag 2.0 kiln efficiency improvements combined with a worker condition improvement (WCI) package designed to enhance occupational safety, improve payment practices, and improve living conditions for kiln workers. The WCI package, finalized during our pilot, is structured around five components: (1) provision of personal protective equipment (PPE) and occupational safety measures, (2) timely wage payment monitoring, (3) improvements to workplace and living conditions, (4) heat mitigation strategies, and (5) child labor awareness and prevention.

Owners in kilns in the intervention arm will receive an integrated ZZK2.0+ training which includes a Zigzag 2.0 refresher training combined with worker condition improvement (WCI) package designed to enhance occupational safety, improve payment practices, and improve living conditions for kiln workers. The WCI package, finalized during our pilot, is structured around five components: (1) provision of personal protective equipment (PPE) and occupational safety measures, (2) timely wage payment monitoring, (3) improvements to workplace and living conditions, (4) heat mitigation strategies, and (5) child labor awareness and prevention.

PPE and occupational safety
The intervention will encourage owners to provide basic safety gear to workers in high-risk roles, including firemen, unloaders, coal crushers, and loaders. Protective equipment includes work boots, gloves, head protection, goggles, cooling towels, masks, and sun caps, all sourced from local markets to ensure availability, sustainability and affordability. First aid kits and oral rehydration salts should also be provided for immediate management of minor injuries and heat-related illnesses. Implementation will be accompanied by systems for procurement support, action planning, monitoring, replacement scheduling, and troubleshooting for owners and workers to support consistent availability and use.

Timely wage payment monitoring
To address the widespread problem of wage delays and deductions, we will encourage owners and their managers to establish a monitoring system for timely payments. This will include promoting weekly record-keeping by managers and sardars, monthly owner–worker discussion meetings, random spot checks by project staffs, and standardized monitoring forms. Transparency can be enhanced by promoting publicly posting payment schedules at kilns. Communication and grievance systems will be established through structured meetings and anonymous reporting channels (e.g our project hotline). Owners will be instructed to work with sardars to encourage timely payments and support fair practices.

Improved living and working conditions
Kilns will be encouraged to construct resting sheds with seating and drinking water provision. These structures will be strategically placed to maximize shade and serve as designated rest areas. Sanitation conditions will be improved through handwashing stations, soap provision, and toilet maintenance. Where feasible, fans will be installed to enhance cooling. Technical guidance will be provided for design and placement, with inspections to ensure proper use and maintenance throughout the season.

Heat Mitigation
Workers will receive training on recognizing symptoms of heat stress, hydration protocols, safe work–rest cycles, and emergency response procedures. Practical demonstrations will cover correct PPE use in hot environments, cooling techniques, and first aid basics. Training will be delivered through group sessions with illustrated posters in Bengali and reinforced by managers through short reminders during peak heat months. Sardars will receive targeted training on supporting work–rest cycles, and families living on-site will receive basic awareness messages to extend protection beyond the workplace.

Child Labor Awareness and Prevention
The intervention will establish also receive information to prevent child labor at kilns. Owners and sardars will be encouraged to collect and verify identity documents (National ID, birth certificate) for all workers. Awareness sessions for parents will be conducted twice per season, focusing on child rights and educational opportunities. Kilns will be encouraged to establish clear penalties for non-compliance, and referral systems will connect children to local education providers.

Training
Training will integrate Zigzag 2.0 refresher content with the WCI package into a single program for kiln owners, and managers. In-person training sessions that combine refresher material on Zigzag 2.0 with action planning on PPE distribution, wage monitoring, and living condition improvements will be delivered in groups of intervention kilns. They will be encouraged by testimonials of other kiln owners who have improved worker conditions in their kilns and see recorded videos from the Ministry of Environment and Labor about the intervention aligning with their policies.

At the kiln level, workers and sardars will receive practical training, focused on heat mitigation and child labor awareness. Owners/ kiln managers/Sardars will receive training on wage monitoring based on improved practices at the kiln. These sessions will be conducted both on-site, using demonstration kilns to provide hands-on experience. Illustrated posters, videos, and practical exercises will reinforce safety protocols, PPE use, hydration practices, and injury reporting. Kilns will reinforce the components of the intervention throughout the season.

2025-12-21

2026-02-22

1. Personal Protective Equipment (PPE) Index
2. Workplace conditions
3. Timeliness of wages
4. Labor trafficking indicators
5.Heat stress

1. Personal Protective Equipment (PPE): We use principal components analysis (PCA) to calculate a continuous PPE index for each worker, using a set of 9 indicators taking a value of 1 if a given worker reports access to a given PPE item (cooling towels, gloves, helmets, head coverings, boots, goggles, masks, first aid support, oral rehydration salt (ORS)), and zero otherwise. Our study is powered at 80% to observe a minimum decline of 0.29 in a PPE index computed using previous season data (standardized effect size of 0.27), with a relatively high ICC of 0.24.
2. Workplace conditions: We use principal components analysis (PCA) to calculate a continuous index reflecting the quality of working conditions each worker reports. Components include sanitation conditions, access to rest areas, cooling sheds, and amenities in living quarters. Our study is powered at 80% to observe a minimum decline of 0.44 in a working conditions index computed using previous season data (standardized effect size of 0.28), given a high leval of intracluster correlation (ICC = 0.39).
3. Timeliness of wages: For each kiln, timeliness of wages is measured using share of workers reporting on-time payment during the preceding 3 months of work (or since the beginning of the season, if shorter than 3 months). Although available data for the timeliness of wages is limited, we estimate a minimum detectable effect size of 7.15 percentage points in the probability of timely pay (a standardized effect size of .22 relative to baseline), given a relatively high ICC of 0.32.
4. Labor trafficking indicators: Conditions contributing to labor trafficking are measured using a standarized set of indicators developed by the United States Department of State Trafficking in Persons Office. The standard tool consists of 39 total indicators (4 extremely strong indicators, 14 strong indicators, and 21 medium indicators) for conditions related to labor trafficking determination. Our survey focuses on a subset of 17 of these indicators deemed culturally appropriate and relevant to the intervention. Our primary outcome is then computed as a continuous measure of the total number of indicators experienced (weighting medium indicators at 0.66). Previous surveys collecting similar data show that our study is powered to detect declines of 0.342 trafficking indicators (an 18% decline; standardized effect size of 0.26) with 80% power at a 5% confidence level.
5. Heat stress: We measure heat stress following standard clinical practice using maximum heart rate, skin temperature, and urine specific gravity. Our study is powered at 80% to observe a minimum decline of 5.43BPM in maximum heart rate (standardized effect size of 0.34), 0.49° in skin temperature (standardized effect size of 0.301), and 0.0022 in USG (standardized effect size of 0.337), assuming a relatively high intracluster correlation of .3 (estimated using data on outcomes related to work conditions measured in a preceding study of the same kilns).

Worker reported health outcomes

Respiratory outcomes: Respiratory health will be assessed through worker-reported symptoms (cough, shortness of breath, chest tightness, wheezing) using structured recall periods of 2 days, 1 week, and 2 weeks prior to survey administration. Symptoms will be scored using frequency categories (none, mild, moderate, severe) and functional impact on work activities. Given the seasonal nature of brick kiln operations and potential recall bias with longer time periods, the 2-day and 1-week windows will serve as primary respiratory endpoints. Based on occupational health studies in similar dusty work environments, we estimate our study has 80% power to detect a 15-20% reduction in moderate-to-severe respiratory symptom reporting (standardized effect size of approximately 0.25), assuming an intracluster correlation similar to our other worker-reported outcomes (ICC ≈ 0.30).

Injuries: Workplace injuries will be measured using worker recall of incidents occurring in the past 2 weeks, categorized by type (cuts, burns, falls, crushing injuries), body part affected, and severity (required stopping work, sought medical care, lost work days). The 2-week recall period balances accuracy of reporting with sufficient observation time to capture injury events. Our sample size provides 80% power to detect a reduction of approximately 8-12 percentage points in injury incidence (standardized effect size of 0.22-0.28), based on baseline injury rates observed in comparable brick manufacturing settings and assuming moderate intracluster correlation (ICC ≈ 0.25).

We will use our database of past enrolled kilns to create a list who have adopted ZZK2.0 in the Jashore, Jhenaidah and Shatkhira districts of Khulna Division, Bangladesh (n = 200). Field teams will approach these kilns, secure their consent to participate in the trial, and conduct a baseline survey. From the enrolled kilns, we will stratify the kilns by phase of prior project participation and randomize kilns into one of 2 groups: intervention (n=120) and control (n=80).

Owners in kilns in the intervention arm will receive an integrated ZZK2.0+ training which includes a Zigzag 2.0 refresher training combined with worker condition improvement (WCI) package designed to enhance occupational safety, improve payment practices, and improve living conditions for kiln workers. The WCI package, finalized during our pilot, is structured around five components: (1) provision of personal protective equipment (PPE) and occupational safety measures, (2) timely wage payment monitoring, (3) improvements to workplace and living conditions, (4) heat mitigation strategies, and (5) child labor awareness and prevention.

PPE and occupational safety
The intervention will encourage owners to provide basic safety gear to workers in high-risk roles, including firemen, unloaders, coal crushers, and loaders. Protective equipment includes work boots, gloves, head protection, goggles, cooling towels, masks, and sun caps, all sourced from local markets to ensure availability, sustainability and affordability. First aid kits and oral rehydration salts should also be provided for immediate management of minor injuries and heat-related illnesses. Implementation will be accompanied by systems for procurement support, action planning, monitoring, replacement scheduling, and troubleshooting for owners and workers to support consistent availability and use.

Timely wage payment monitoring
To address the widespread problem of wage delays and deductions, we will encourage owners and their managers to establish a monitoring system for timely payments. This will include promoting weekly record-keeping by managers and sardars, monthly owner–worker discussion meetings, random spot checks by project staffs, and standardized monitoring forms. Transparency can be enhanced by promoting publicly posting payment schedules at kilns. Communication and grievance systems will be established through structured meetings and anonymous reporting channels (e.g our project hotline). Owners will be instructed to work with sardars to encourage timely payments and support fair practices.

Improved living and working conditions
Kilns will be encouraged to construct resting sheds with seating and drinking water provision. These structures will be strategically placed to maximize shade and serve as designated rest areas. Sanitation conditions will be improved through handwashing stations, soap provision, and toilet maintenance. Where feasible, fans will be installed to enhance cooling. Technical guidance will be provided for design and placement, with inspections to ensure proper use and maintenance throughout the season.

Heat Mitigation
Workers will receive training on recognizing symptoms of heat stress, hydration protocols, safe work–rest cycles, and emergency response procedures. Practical demonstrations will cover correct PPE use in hot environments, cooling techniques, and first aid basics. Training will be delivered through group sessions with illustrated posters in Bengali and reinforced by managers through short reminders during peak heat months. Sardars will receive targeted training on supporting work–rest cycles, and families living on-site will receive basic awareness messages to extend protection beyond the workplace.

Child Labor Awareness and Prevention
The intervention will establish also receive information to prevent child labor at kilns. Owners and sardars will be encouraged to collect and verify identity documents (National ID, birth certificate) for all workers. Awareness sessions for parents will be conducted twice per season, focusing on child rights and educational opportunities. Kilns will be encouraged to establish clear penalties for non-compliance, and referral systems will connect children to local education providers.

Training
Training will integrate Zigzag 2.0 refresher content with the WCI package into a single program for kiln owners, and managers. In-person training sessions that combine refresher material on Zigzag 2.0 with action planning on PPE distribution, wage monitoring, and living condition improvements will be delivered in groups of intervention kilns. They will be encouraged by testimonials of other kiln owners who have improved worker conditions in their kilns and see recorded videos from the Ministry of Environment and Labor about the intervention aligning with their policies.

At the kiln level, workers and sardars will receive practical training, focused on heat mitigation and child labor awareness. Owners/ kiln managers/Sardars will receive training on wage monitoring based on improved practices at the kiln. These sessions will be conducted both on-site, using demonstration kilns to provide hands-on experience. Illustrated posters, videos, and practical exercises will reinforce safety protocols, PPE use, hydration practices, and injury reporting. Kilns will reinforce the components of the intervention throughout the season.

Stratified randomization done in an office on a computer.

Unit of randomization is a brick kiln, all workers within a kiln are treated, as the training is delivered to the kiln owners and managers.

Yes

200 brick kilns

1000 kiln workers

120 brick kilns in the treatment arm, 80 brick kilns in the control arm.

Our study is powered at 80% to observe a minimum decline of 0.29 in a PPE index computed using previous season data (standardized effect size of 0.27), with a relatively high ICC of 0.24. Our study is powered at 80% to observe a minimum decline of 0.44 in a working conditions index computed using previous season data (standardized effect size of 0.28), given a high leval of intracluster correlation (ICC = 0.39). Although available data for the timeliness of wages is limited, we estimate a minimum detectable effect size of 7.15 percentage points in the probability of timely pay (a standardized effect size of .22 relative to baseline), given a relatively high ICC of 0.32. Our study is powered to detect declines of 0.342 labor trafficking indicators (an 18% decline; standardized effect size of 0.26) with 80% power at a 5% confidence level. Our study is powered at 80% to observe a minimum decline of 5.43BPM in maximum heart rate (standardized effect size of 0.34), 0.49° in skin temperature (standardized effect size of 0.301), and 0.0022 in USG (standardized effect size of 0.337), assuming a relatively high intracluster correlation of .3 (estimated using data on outcomes related to work conditions measured in a preceding study of the same kilns).