Developing Effective Protocols to Protect Farmworkers from Heat Stress and Illness While Working in Polytunnels

Isabella Kaser^1,*, Maripaula Valdes-Berriz², Annemiek C. Schilder², Maureen McGuire³, Catherine Carpenter¹, Ellen Brokaw⁴, Michael Dimock⁵, Gina M. Solomon⁶

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Published in Journal of Agricultural Safety and Health 31(1): 15-30 (doi: 10.13031/jash.16111). Copyright 2025 American Society of Agricultural and Biological Engineers.

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¹ Tracking California, Public Health Institute, Oakland, California, USA.

² University of California Cooperative Extension, Ventura County, Ventura, California, USA.

³ Farm Bureau of Ventura County, Ventura, California, USA.

⁴ Brokaw Nursery, Ventura, California, USA.

⁵ Roots of Change, Public Health Institute, Oakland, California, USA.

⁶ Division of Occupational, Environmental & Climate Medicine, UCSF School of Medicine, San Francisco, California, USA.

^* Correspondence: isabella.kaser@trackingcalifornia.org

The authors have paid for open access for this article. This work is licensed under a Creative Commons Attribution NonCommercial NoDerivatives 4.0 International License https://creative commons.org/licenses/by nc nd/4.0/

Submitted for review on 24 June 2024 as manuscript number JASH 16111; approved for publication as a Research Brief by Community Editor Dr. Michael Pate of the Ergonomics, Safety, & Health Community of ASABE on 24 October 2024.

Citation: Kaser, I., Valdes-Berriz, M., Schilder, A. C., McGuire, M., Carpenter, C., Brokaw, E., … Solomon, G. M. (2025). Developing effective protocols to protect farmworkers from heat stress and illness while working in polytunnels. J. Agric. Saf. Health, 31(1), 15-30. https://doi.org/10.13031/jash.16111

Highlights

• Farmworkers are at high risk of heat-related illness, especially those working in polytunnels.
• There is a gap in knowledge regarding working conditions inside polytunnels.
• Polytunnels are prevalent in California’s Central Coast region.
• Recommendations to reduce the risk of heat-related illness among workers in polytunnels were formulated.

Abstract. Polytunnels—also known as hoop houses—are used worldwide to grow certain crops year-round, primarily to protect plants from precipitation and cool temperatures. Farmworkers may be at increased risk in polytunnels due to higher temperatures and relative humidity. In the Central Coast region of California, polytunnels are commonly used to grow berries and other crops, but information on measures used to reduce heat stress in farmworkers working in polytunnels or how many workers are potentially exposed to these conditions is scarce. The purpose of this study was to: (1) estimate the area under polytunnels and the number of workers in them in California’s Central Coast region; (2) assess current practices to manage heat and protect workers in polytunnels; and (3) use this information to develop proposed best practices for protecting farmworkers in polytunnels. Using satellite imagery and crop production records, the area under polytunnels in the region was estimated at 5,162 ha with a conservatively estimated 46,000 farmworkers. Through key informant interviews, we found that farms are generally following OSHA worker safety regulations. However, additional measures may be needed to protect workers because environmental conditions inside polytunnels are variable and difficult to predict. For instance, wet bulb globe temperature would be a more accurate measure of heat stress risk than temperature alone. We propose recommendations that follow the hierarchy of controls to reduce the risk of heat-related illness among workers inside these structures.

Keywords.Agricultural health and safety, Farmworker health, Heat illness prevention recommendations, Hoop houses, Polytunnels.

Agricultural workers in the United States are over 35 times more likely to die of heat-related illness than other workers (United States Joint Economic Committee Democrats, 2024). Heat illness in farmworkers is multifactorial, depending on external conditions as well as individual factors such as exertion, temperature, and hydration status (NIOSH, 2016). Climate change is projected to increase the number and duration of extreme heat events and therefore will likely increase the risk of occupational heat-related illnesses (US EPA, 2022; United States Joint Economic Committee Democrats, 2024). One factor that may be controllable is the work environment.

An increasingly common work environment in agriculture throughout the Central Coast of California, United States, is a structure called a polytunnel or hoop house. Polytunnels are rounded structures consisting of metal or polyvinyl chloride(PVC) frames covered with polyethylene plastic (figs. 1a, 1b, 1c, 1d). The ends and sides are usually open, but can be closed in cold climates or seasons. Polytunnels are cheaper and easier to build than greenhouses and can be more flexible to use. These structures protect plants from precipitation, wind, ultraviolet light, and low temperatures (Gu, 2021). They are used to grow a wide range of agricultural and horticultural crops and can significantly extend the growing season in cold climates (Gu, 2021; Lee et al., 2019). In the Central Coast region of California (Santa Cruz, San Benito, Monterey, San Luis Obispo, Santa Barbara, and Ventura Counties), polytunnels are used to grow raspberries, blackberries, blueberries, strawberries, tomatoes, flowers, and hemp (Harkleroad, 2020).

Because polytunnels act as a greenhouse, the air temperature inside polytunnels can become hotter than the air temperature outside. Solar radiation penetrates the plastic cover of the polytunnel, is absorbed by plants and other surfaces, and then emitted as heat, which is trapped in the structure (Robson et al., 2022). Relative humidity (RH) may also impact the perceived temperature inside polytunnels (Lee et al., 2019). While these conditions affect both plants and farmworkers, plants can thrive under conditions that are adverse for people.

Temperatures inside polytunnels may become more extreme due to climate change, especially in Ventura County, which is one of the fastest-warming counties in the United States (US EPA, 2022; Mufson et al., 2019). Because farmworkers are more likely to develop heat-related illnesses than any other workers in the U.S. (NIOSH, 2016) and with temperatures expected to rise due to climate change, farmworkers may be more vulnerable while working in polytunnels.

Figure 1. (a) Polytunnels used to grow blackberries and raspberries; (b) raspberries growing in a polytunnel; (c) blackberries in a polytunnel; and (d) rows of polytunnels with blackberries in Ventura County, California, US. (Photos courtesy of A. Schilder).

Materials and Methods

Polytunnel and Farmworker Estimates

There are no records of how many polytunnels are used in the United States; therefore, an estimate of the number of polytunnels is needed to estimate the number of workers. To estimate the hectarage under polytunnels on the Central Coast, the California Department of Water Resources (DWR) 2020 crop mapping dataset was used (DWR, 2023). All land uses classified as having truck, nursery, and berry crops as the main-season crop were selected because many of these crops are grown in polytunnels. These categories represent aggregated groups of specific crop types that DWR uses to classify land use. Of the truck crop category (e.g., tomatoes, peppers, lettuce, leafy vegetables, carrots, and broccoli), tomatoes are most likely to be grown in polytunnels.

The land use polygon boundaries (fig. 2) were overlaid on Esri’s (Environmental Systems Research Institute, Inc., Redland, CA) world satellite imagery, captured between 2020 and 2022, to visually confirm and further refine the selected areas that contained polytunnels. The total number of hectares with polytunnels was calculated by crop category and county. Areas with polytunnels with the crop category “bush berries” were compared to the California Department of Pesticide Regulation's (CDPR) Pesticide Use Reporting (CDPR, 2023) at the section level (1.6x1.6-km geographic area) in order to verify the type of berries (blackberries, blueberries, or raspberries) grown. Land uses with multiple crops planted throughout the year and unclassified land uses were included in cases where polytunnels covered all or a portion of the land area observed on satellite imagery. The number of workers that may be regularly working inside polytunnels was estimated based on the number of hectares of the main crop identified in the final land-use spatial dataset multiplied by the average number of workers per hectare per year estimated for that crop. For example, 12.5 workers per hectare for bush berries, 5.0 workers per hectare for strawberries, and 0.5 workers per hectare for nursery crops based on information provided by the Farm Bureau of Ventura County (M. McGuire, pers. comm.) and the University of California Cooperative Extension (E. Takele, pers. comm.). For truck crops, specifically tomatoes, an average of 2.0 workers per ha is estimated, based on 1.5 workers per ha regularly and double that during harvest (TAMU, n.d.).

Figure 2. Satellite imagery of polytunnels with land use boundaries (outlined in blue) in Santa Cruz County, CA. Image captured from Esri on June 16, 2020.

Key Informant Interviews

To better understand current field practices to manage heat and reduce the risk of heat stress in farmworkers, key informant interviews were conducted in Ventura County. Key informants (participants) included farm managers, irrigation managers, field supervisors, and safety coordinators at both small and large operations. Ventura County was selected as the study location because it has the most polytunnel hectarage in the region. Furthermore, Ventura County has been impacted significantly by extreme heat events in recent years, raising concerns about farmworker health. Lastly, members of the study team have trusted working relationships with agricultural industry leaders in the county.

Participants were selected to represent a range of crops and operation sizes using polytunnels in Ventura County. Once contact was established with potential key informants, the project’s objectives and confidentiality measures were described and explained, and a copy of the questionnaire was provided. The interviews were conducted in person or by phone in English or Spanish. Interview questions in English are available in the appendix. The questionnaire included open-ended and multiple-choice questions. Answers were analyzed by extracting information from individual responses, grouping responses into relevant categories, and using nominal scales to summarize counts. Because participants were interviewed strictly in their professional capacity and the questions were exclusively about company practices, the interviews were determined by the Public Health Institute Institutional Review Board (IRB) not to be human subject research.

Table 2. California Department of Water Resources (DWR) land use crop categories[a] in areas with polytunnels identified by satellite imagery[b] in counties on the Central Coast in California.
No. Hectares with Polytunnels by Crop Category	Monterey	San Benito	San Luis Obispo	Santa Barbara	Santa Cruz	Ventura	Total ha (%)
Bush berries[c]	321	16	93	410	835	1713	3387 (66%)
Truck crops[d]	79	71	88	335	59	145	777 (15%)
Flowers and nursery crops	199	2	42	32	56	161	491 (10%)
Strawberries	13	0	128	78	9	139	368 (7%)
Other crops[e]	14	5	11	4	0	31	66 (1%)
Unclassified	11	0.4	0	26	3	32	72 (1%)
Total	638	95	363	884	961	2220	5,162
[a] DWR (2023). [b] Environmental Systems Research Institute, Inc., Redland, CA [c] Bush berries include blackberries, blueberries, raspberries, and boysenberries. [d] Truck crops include tomatoes, peppers (chili, bell, etc.), cole crops (broccoli, cabbage, cauliflower, Brussels sprouts), lettuce and leafy greens, and carrots. [e] Other crops include beans (dry), miscellaneous truck, grain, hay, and grasses.

Results and Discussion

Polytunnel and Farmworker Estimates

In California’s Central Coast region, we estimated 5,162 ha of polytunnels using satellite imagery (table 2). Specific crop categories identified by DWR on land with polytunnels included bush berries, strawberries, flowers, nursery, and truck crops. Over 3,387 ha (66% of the total area under polytunnels) contained bush berries, defined by the Workers’ Compensation Insurance Rating Bureau of California (2023) as raspberries, blackberries, blueberries, and boysenberries. Bush berries were the dominant crop in all counties, except San Benito County. Approximately 777 ha (15% of the total) under polytunnels contained truck crops, 491 ha (10% of the total) contained flowers and nursery crops, and 368 ha (7% of the total) grew strawberries. Based on the average number of workers per hectare required to farm certain crops (M. McGuire, pers. comm.; E. Takele, pers. comm.; Texas A&M University, Aggie Horticulture (TAMU), n.d.), the number of workers farming bush berries inside polytunnels is estimated at 42,338 in the Central Coast region. For strawberries in polytunnels, the number of workers is estimated at 1,840, while for flower and nursery crops it is 246. For truck crops, the number of workers is estimated at 1,554, assuming that most of the land use contained polytunnels for tomatoes. The number of workers for “other” or “unclassified” crops (138 ha) was not calculated but is likely to be at least 100. Thus, the total number of workers regularly present in polytunnels in the Central Coast region of California is estimated to be around 46,000. However, the actual number of workers exposed to polytunnel conditions for shorter periods may be much higher, such as during harvest, planting, and pruning. The total number of workers who spend some time working in polytunnels during the year in this region may reach several hundred thousand. For instance, the number of workers needed to harvest strawberries and blueberries ranges from 25–37 workers per hectare (TAMU, n.d.). In raspberries and blackberries, fruit is harvested two to three times per week for up to six months (O. Daugovish, pers. comm.).

Key Informant Interviews

It was challenging to find participants due to hesitancy to share information related to worker safety protocols. A total of 12 employees were contacted, some from the same or affiliated companies, to reach a sample size of five interviews. The participants were from four companies that represent about 40% of the area under polytunnels in Ventura County. These companies grow strawberries, raspberries, blackberries, blueberries, and flowers, and vary greatly in size, ranging from less than 10 ha to about 800 ha under polytunnels. The positions of those interviewed included farm managers, irrigators, field supervisors, safety directors, and production managers. All participants had more than 5 years of experience in the industry.

The size of the polytunnels varied depending on the plants grown inside and was variable between participating farms. Polytunnels ranged from 5–10 m wide and 3–8 m tall. Flower tunnels were the shortest, while the tallest tunnels were used to grow strawberries. The position of the polytunnels was determined by three main criteria: sun direction, wind direction, and practical considerations, such as field size, shape, and maximizing production.

All participants open the sides of polytunnels to increase ventilation, and four open ventilation gaps at the top. None of the participants reported using fans in polytunnels. The use of shade cloth was also uncommon (n = 2) and was only used at packing stations. However, three participants reported using chalk paint on the plastic to increase shading and to reflect sunlight. The use of special plastics was reported by three of the respondents for obtaining the desirable amount of shading, light, and/or durability. Adjusting plant spacing, plant density, and canopy size was mentioned by one participant to reduce heat and humidity. The placement of gaps and open spaces between polytunnels varied considerably, as some reported shaded gaps between blocks, while others reported 3-m distances between the ends of polytunnels. Some interviewees countered that these gaps did not allow them to control the temperature when heat was desirable for plant growth. High temperatures were less of a concern for the flower growers than low temperatures.

Temperature was only measured regularly when it was predicted to be high outdoors. When the temperature was high, one participant reported measuring temperature every hour inside the polytunnels, but others did not mention a specific frequency. At least two interviewees reported having mercury and digital thermometers outside the polytunnels. Only one participant monitored RH using a Kestrel weather meter, and another two reported using online weather applications. The person responsible for monitoring the temperature and RH inside the polytunnels was highly variable. No one was aware of the Wet Bulb Globe Temperature (WBGT).

Other procedures to prevent heat stress were more common, such as changing work hours, having paid breaks, and providing cold water. The outside temperature threshold at which workers would stop laboring inside the polytunnels was also highly variable: 24–27°C, over 27°C, 32°C, and 35–38°C. Four of the participants reported that they did not use the National Weather Service Heat Index to determine when to stop working. Three participants reported that when the temperature was high, workers self-monitored if they needed additional breaks and could take them when needed. The other interviewees indicated they gave workers the breaks stated by the California Heat Illness Prevention in Outdoor Places of Employment regulation (Cal/OSHA, 2024). One company reported making breaks mandatory when the temperature was “very high.” None of the companies provided special clothing (e.g., cooling vests, caps with fans), but one company reported that branded clothing was always made with materials that were appropriate for the weather (e.g., light-colored and cooling materials for hot conditions), although it was not regularly provided. A second participant reported that sometimes they provide wet paper towels.

All participants reported that supervisors were trained to prevent and recognize symptoms of heat stress, and at least four provided training to their workers (e.g., during morning meetings). Supervisors and safety teams oversaw monitoring for heat stress at three companies; workers were also encouraged to observe and report issues at two companies; one participant did not respond, and one reported they had never had issues with heat stress at their company.

Challenges identified by survey participants were around perceived worker behavior (not drinking enough water or taking enough breaks) and a lack of written guidelines and recommendations specifically related to heat stress prevention in polytunnels. General recommendations made by participants were to protect workers by having strict cut-off times for working inside polytunnels, ensuring that workers are educated on heat stress, using taller polytunnels to increase ventilation, utilizing shading paints, providing cold water that is easily accessible, and having emergency procedures with specific protocols.

Discussion

Given that polytunnels are relatively common in the Central Coast region of California, tens of thousands of workers may be exposed to conditions that are not being measured appropriately. Key informant interviews in Ventura County showed that although both large and small companies follow California Heat Illness Prevention in Outdoor Places of Employment regulations (Cal/OSHA, 2024), current practices might not be sufficient to reduce the risk of heat stress in farmworkers working in polytunnels. For example, despite some awareness of potential heat risks, none of the participants reported consistent monitoring of temperature and humidity inside the polytunnels or using tools such as the Heat Stress Index or Wet Bulb Globe Temperature to assess heat stress risk. These indicate that additional training and use of environmental monitoring tools may increase precision in heat risk management. While interviews were only conducted in Ventura County and management protocols may not be representative of the entire Central Coast or California as a whole, we believe them to be fairly typical since the larger companies operate throughout the region. Given the concerns about heat stress in polytunnels, future research and education efforts could be expanded to other counties on the Central Coast.

With limited published research and data on the actual temperatures and relative humidity inside polytunnels in the region, it makes it difficult to know what working conditions are like for those inside these structures. Additional studies to monitor environmental conditions in polytunnels will help clarify the level of heat risk faced by farmworkers. There is also a lack of informational resources including written guidelines and recommendations for farmworkers related to heat stress prevention in polytunnels. Further research is needed to better understand the number of people affected and to enhance interventions that reduce heat stress risk among farmworkers.

To address the lack of resources and guidance for workers, we developed a set of recommendations specific to the polytunnel environment based on the reviewed literature and results from the interviews (table 3). In addition, Cal OSHA’s Heat Illness Prevention Plan (Cal/OSHA, 2024) and the University of California Agriculture and Natural Resources (University of California Agricultural and Natural Resources, 2015) Heat Illness Prevention Program were both used to inform the recommendations. Controlling farmworkers’ exposure to heat in the workplace is essential to protect their health and safety. The hierarchy of controls is a tool used to control exposure to hazards in the workplace to protect workers and can be used to lower exposure and reduce risk of illness (NIOSH, 2023). Therefore, the recommendations follow the hierarchy of controls to reduce the risk of heat-related illness in workers inside polytunnels. The proposed control methods are placed in order from most to least effective (elimination, substitution, engineering controls, administrative controls, PPE). These recommendations include improving ventilation and air circulation in tunnels, applying shade cloth or paint to lower irradiance and temperature in polytunnels, measuring WBGT with installed or handheld instruments, providing additional worker training, and ensuring the use of personal protective equipment. The recommendations will be developed into informational resources for workers and companies.

Conclusions

Farmworkers represent a population at heightened risk of heat-related illnesses, a risk that may be exacerbated by climate change and working in polytunnels due to the higher temperatures and RH compared to outdoor environments. Despite the widespread use of polytunnels in agriculture, particularly in California’s Central Coast region, there are insufficient data on environmental conditions in these structures, the number of workers regularly working within them, and the incidence rates of heat-related illnesses in this context. More research is needed to accurately measure environmental variables, predict heat stress risk, and evaluate the accuracy and efficacy of heat stress assessment tools inside polytunnels. Furthermore, training of farm staff and farmworkers on the effective use of heat stress prediction tools and mitigation methods in polytunnels is recommended.

Acknowledgments

Funding for this project was provided by Cigna (Achieving Resilient Communities Project: Conducting Assessments and Capacity Building to Improve Health) and the University of California (UC) Thelma Hansen Fund. The authors thank interview participants for their willingness to be interviewed on their current practices. We also thank Maureen McGuire from the Farm Bureau of Ventura County and Etaferahu Takele from UC Cooperative Extension, San Bernardino County, for worker estimates in different crops. We are grateful to the following members of the Achieving Resilient Communities team: Lesley Kroupa, Doris Meier, and Alexander Nikolai for their support of the project. We also thank

Table 3. Recommendations to reduce the risk of heat-related illness in workers inside polytunnels.
Control Category	Control Method	Control Description
Engineering Controls	Increase ventilation	Circulating fans, opening vents, or removing the polyethylene coverings (Ge et al., 2021; USDA, 2014). Roll up sides and end-wall coverings (Biernbaum, 2013). Change position, size or shape of structure, and number of open areas/vents.
	Reduce irradiance	Use shade cloth or other types of cladding materials or chalk paint (Caruso et al., 2020; Daugovish and Larson, 2008; Robson et al., 2022; Singh et al., 2013; Soni et al., 2005). Reuse weathered polyethylene as plastic sheeting becomes opaque with age. Daytime temperatures may be a few degrees lower inside than outside due to reduced irradiance (Daugovish and Larson, 2008).
	Reduce humidity	Reduce plant density and height to facilitate airflow and reduce humidity. Time crop irrigation to reduce evaporation during hours of highest temperature and avoid excess watering and pooling (University of Massachusetts Amherst, 2022).
Administrative Controls	Monitor environmental conditions	Place wet bulb globe temperature (WBGT) dataloggers in structures to increase measurement accuracy (NIOSH, 2016; Villagrán et al., 2021). Use portable, hand-held heat stress indicator devices based on WBGT. When WBGT is not available, use the Heat Index with an alert threshold of 26.7°C (80°F) (Cooper et al., 2017). Assign dedicated personnel to monitor and record environmental conditions inside polytunnels on a regular basis and to maintain monitoring equipment.
	Training	Provide supervisors and workers strategies to reduce heat impacts, recognize the signs and symptoms of heat-related illness, and how to respond to heat-related illness. Provide training on the company’s process to identify and address safety hazards.
	Scheduling	Rotate workers in and out of polytunnels throughout the day. Change work hours to avoid work inside polytunnels during the hottest time of day. Require workers to take scheduled breaks outside of the polytunnels and to take extra breaks when needed. Schedule maximum periods of time workers can be inside polytunnels. Additional considerations should be made for workers not acclimated to the heat.
Personal Protective Equipment	Cooling clothing	Provide workers with a combination of cooling vests and bandanas to protect them against heat-related illness (Chicas et al., 2020). Wetted overgarments, such as cotton coveralls, are an inexpensive tool that may provide cooling in low-humidity and high-temperature conditions (NIOSH, 2016). Wetted cooling garments might be the most effective for light to moderate work (Sarkar and Kothari, 2014) and provide a cooling effect in both dry and wet environments (Xu et al., 2006). Water evaporation garments (caps, vests, clothing) also exist but may limit movement (NIOSH, 2016).

partner organizations Good Farms, Inc., the Central Coast Alliance United for a Sustainable Economy (CAUSE), and Dr. Oleg Daugovish from UC Cooperative Extension in Ventura County who advised the team on the work.

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Appendix

Questionnaire Used to Guide Interviews

Interview on Management Practices for Heat Stress and Illness Prevention in Agricultural Workers in Polytunnels in Ventura County – September 2022

The purpose of this interview is to identify the most effective practices to protect workers from becoming heat stressed or ill while working in hoop structures or polytunnels. We hope to learn from you what you are currently doing, what has worked for you in the past, and what information we can provide to improve your protocols or procedures to prevent heat illness in your workers. Based on these interviews, we will develop a manual of best management practices that will be distributed to growers in Ventura County. This interview is being conducted by the University of California Cooperative Extension, Ventura County, in collaboration with the Farm Bureau of Ventura County, and Achieving Resilient Communities, a project of the Public Health Institute.

We want to learn as much as possible from you and your experience, so please be honest. The information collected during this interview, including your name and the name of your organization/ company will be kept confidential. Your responses will be compiled into general recommendations and no identifying information will be included in the final product. If you agree to be recorded, the audio from this interview will be transcribed by me to make sure I do not miss any details, and will be immediately deleted. You have the right to stop your participation in this interview at any time or ask for information to not be included, even after the interview has concluded. You can also contact me if you have any questions after the interview (provide business card).

Date:_______________________ Initials of Interviewer:___________________

Q1. What is your name, position, and farm, location?

Name:____________________________________________

Position:__________________________________________

Farm:____________________________________________

Location:_________________________________________

Q2. Please tell me about your experience farming with polytunnels:

a. Where are your polytunnels located?___________________________________

b. What crops do you grow in the polytunnels?_____________________________

c. How many polytunnels do you have? Number_________ and/or Acreage______

d. What size and height are your polytunnels?______________________________

e. For how many years (approximately) have you been farming with polytunnels?_

Q3. How do you manage temperature and relative humidity in polytunnels?

• Open up the sides
• Ventilation gaps
• Orientation of the tunnels in wind direction
• Fans
• Swamp cooler
• Shade cloth over the top
• Using special type of plastic. What type?_______________________________
• Increasing plant spacing
• Reducing plant or canopy size
• Other:___________________________________________________________

Q4. How do you monitor temperature and/or relative humidity in polytunnels?

• We don’t
• By feel
• Rely on weather forecast for outside conditions
• Thermometer: ____Mercury ____Digital
• RH meter
• Sensor that shows both temperature and relative humidity
• Weather station. Data visible_______ or Need to be downloaded_______
• Heat stress meter/Wet bulb globe temperature meter
• An online tool or calculator
• Other____________________________________________________________

Q5. How often do you check conditions in the polytunnels?_______________________

Q6. Who is in charge of monitoring the temperature and relative humidity in the polytunnels, the workers, a supervisor or someone else?_____________________________

Q7. What procedures/protocols do you use to prevent heat stress in workers in polytunnels?

• Change work hours. What hours are typical?____________ How do they change when it is hot? _______________________
• Stop working when a certain threshold temperature is reached inside the polytunnel. What temperature?__________________________________________
• Use the National Weather Service Heat Index to determine when to stop working. What is your threshold?____________________________ Can show chart here for illustration.
• Rest breaks in cool/shaded area.
• How frequent and how long are the breaks?____________________________
• Are these paid breaks?_____________________________________________
• Provide plenty of drinking water on site.
• How close is the watering station?____________________________________
• How do you keep the water cold?____________________________________
• Have a supervisor in charge of monitoring heat stress symptoms in workers. What are next steps if heat stress symptoms are detected?__________________ ________________________________________________________________
• Train the workers about heat stress.
• Provide workers with special clothing (e.g., cooling vests, caps with fans)_____ ________________________________________________________________
• Other:___________________________________________________________

Q8. Are the protocols or procedures you use for worker heat stress prevention in polytunnels the same as those for workers in the field? ___________________________

If no, why not?_______________________________________________________

Q9. Are your protocols for workers in polytunnels verbal or written?__________ Would you be willing to share a copy?__________________________________________

Q10. What recommendations do you have, if any, for other farmers on how best to deal with heat in polytunnels?_______________________________________________

___________________________________________________________________

Q12. Are you interested in receiving additional information about heat stress prevention and protection?______________ How would you prefer to receive this information?____________________________________________________________

Q14. Please share any final thoughts on heat stress prevention and polytunnels.________

___________________________________________________________________

Thank you very much for participating in this interview. Your responses will help in-form how workers can be better protected from heat stress and illness in polytunnels. Please contact me if you have any additional questions or concerns.