Research by Assistant Professor of Public Policy R. Jisung Park was cited in a Vice article about Biden administration plans to establish a federal standard to protect workers from extreme heat. Park led a study that analyzed worker compensation records and found that hotter temperatures are associated with an estimated 20,000 additional injuries per year in California. Workers are prone to poorer cognition and decision-making on hotter days, and days above 90 degrees Fahrenheit come with a 6% to 9% increase in the risk of worker injury, the study found. Park shared his data at a congressional hearing in July. In announcing the new federal safety standards, the Biden administration noted that essential jobs with high exposure levels to heat are disproportionately held by Black and brown workers. The Occupational Safety and Health Administration is now leading a multi-agency effort designed to limit heat illness, injury and death in the workplace.
Assistant Professor of Public Policy R. Jisung Park was featured in an LAist article discussing his research on the effects of rising temperatures on the labor force. California’s Division of Occupational Safety and Health (Cal/OSHA) requires employers to give employees water, rest and shade while working in the heat, but the agency is chronically understaffed and underfunded. Meanwhile, reports of heat-related illness and death continue as temperatures rise. Using a computer model of temperature increases over 20 years and workers’ compensation claims, Park estimated that heat contributes to illness or injury among at least 15,000 California workers each year. He explained that many injuries are misclassified and are not necessarily categorized as heat-related, even if they should be. Park added that heat illness can occur at lower temperatures than expected, and that workers have reported experiencing heat exhaustion on days with temperatures as low as 75 degrees.
A Science News article on the effects of extreme heat on human behavior cited research by R. Jisung Park, assistant professor of public policy. As temperatures rise, violence and aggression also go up while focus and productivity decline, the article noted, adding that lower-income people and countries are likely to suffer the most. “The physiological effects of heat may be universal, but the way it manifests … is highly unequal,” Park said. The article described Park’s research into the impact of hot days on student performance on standardized tests. One of his studies found that students in schools without air conditioning scored lower than would have been expected, and that Black and Hispanic students were more likely to attend school and test in hotter buildings compared to their white counterparts. A separate study by Park, described in Safety+Health magazine, found that hotter temperatures are linked to a significant increase in the risk of workplace injuries and accidents.
Research into the effects of hot weather on workplace injuries, led by Assistant Professor of Public Policy R. Jisung Park, drew widespread media attention. Park’s study found that extreme heat causes many times more workplace injuries than official records capture and that those injuries are concentrated among the poorest workers — the latest evidence of how climate change worsens inequality. Hotter days lead to an additional 20,000 workplace injuries each year in California alone, not just among people who work outdoors but also for indoor workers, endangering those employed in manufacturing, warehousing and wholesale, the study found. High temperatures were linked to injuries from falling, being struck by vehicles or mishandling machinery, in addition to heat stroke, suggesting that heat makes it harder to concentrate. “Hotter temperatures … appear to have hidden costs,” Park told the Los Angeles Times. Several other news outlets also showcased the research, including the New York Times, the Guardian, Marketplace and Vox.
A UCLA study published today shows that hot weather significantly increases the risk of accidents and injuries on the job, regardless of whether the work takes place in an indoor or outdoor setting.
The report is based on data from California’s workers’ compensation system, the nation’s largest.
“The incidence of heat illnesses like heat exhaustion and heat stroke definitely go up on hotter days,” said the study’s lead researcher R. Jisung Park, an assistant professor of public policy at UCLA Luskin. “But what we found is that ostensibly unrelated incidents — like falling off a ladder or being hit by a moving truck or getting your hand caught in a machine — tend to occur more frequently on hotter days, too.”
By comparing records from more than 11 million California workers’ compensation claims from 2001 to 2018 to high-frequency local weather data, Park and his co-authors isolated the impact of hotter days on the number of injury claims.
The study shows that on days with high temperature above 90 degrees Fahrenheit, workers have a 6% to 9% higher risk of injuries than they do on days with high temperatures in the 50s or 60s. When the thermometer tops 100, the risk of injuries increases by 10% to 15%.
Those findings are particularly alarming in the context of climate change, which is expected to produce more high-temperature days each year. The researchers estimate that high temperatures already cause about 15,000 injuries per year in California.
“Heat is sometimes described as a silent killer,” said Nora Pankratz, a UCLA postdoctoral scholar. “But if you look into the data and do the statistical analysis, you find that heat has a significant impact on mortality and health outcomes.”
It’s not surprising that hot weather would lead to injuries and illness among workers in predominantly outdoor industries such as agriculture, utilities and construction. But the data consistently show that industries in which most people work indoors are affected as well. In manufacturing, for example, days with high temperatures above 95 degrees have an injury risk that is approximately 7% higher than days with high temperatures in the low 60s.
“A lot of manufacturing facilities are not air conditioned,” said Stanford University postdoctoral scholar A. Patrick Behrer, the study’s other co-author. “Because you’re inside, you don’t necessarily think about the temperature as being a major threat.”
The reality is that overheated workers face numerous risks, regardless of where the work occurs.
“Heat affects your physiology,” Park said. “It affects your cognition. It affects your body’s ability to cope. It seems possible that what we’re observing in the data for these workers is that they’re more likely to make mistakes or errors in judgment.”
The researchers found that heat-related workplace injuries are more likely to be suffered by men and lower-income workers. In addition, younger people suffer more heat-related injuries, possibly in part because they’re more likely to hold jobs with greater physical risks on construction sites, in manufacturing plants or at warehouses.
For an office worker at a computer desk, nodding off on a hot summer afternoon is unlikely to cause an injury. “But if you have a huge chainsaw in your hand, you’re not in a great situation,” Park said.
Among the paper’s other conclusions:
- The number of heat-related injuries actually declined after 2005, when California became the first state to implement mandatory heat illness prevention measures for outdoor workplaces on days when temperatures exceed 95 degrees.
- The financial costs of heat-related injuries may be between $750 million and $1.25 billion per year in California alone, considering health care expenditures, lost wages and productivity, and disability claims.
- Inequalities in the labor market are exacerbated in part by the fact that low-income communities tend to be situated in hotter parts of the state. People in the state’s lowest household income tier are approximately five times more likely to be affected by heat-related illness or injury on the job than those in the top income tier, the study found.
The UCLA Luskin Center for Innovation, where Park is associate director of economic research, provided funding for the study. It is available now through the Institute of Labor Economics, which disseminates working versions of potentially influential research prior to publication in academic journals. Park previewed the findings July 15 during testimony at a Congressional hearing organized by the House Select Committee on the Climate Crisis.
The new study echoes the results of a 2019 study that focused on how extreme temperatures raise injury risk in Texas and in the U.S. mining industry. Park, whose prior research includes a finding that student learning is negatively impacted by warm temperatures, said there has been “an explosion of research just in the last five to 10 years that illustrates, using data, the serious consequences of climate change for health, productivity and economic growth. This likely adds to that urgency of reducing greenhouse gas emissions now.”
Pankratz got involved in the study while working at UCLA Luskin as a postdoctoral scholar, having previously researched the impact of heat on businesses while working toward her Ph.D. in the Netherlands.
Worldwide, she said, there is growing interest in the concept of adaptation — the pragmatic changes that can be made by governments and businesses to cope with the reality of climate change.
“For a long time, the focus has been on mitigation — what can we do to prevent climate change,” she said. “But as it becomes more and more obvious that there is policy inertia on mitigation, it’s important to think about what we can do to adapt and to work as well as possible in a warmer world.”
The study authors, all of whom have backgrounds in economics, realize that the desire to protect workers from heat may be complicated by economic reality.
Behrer said policymakers could stipulate that workers not be exposed to the heat on days above 100 degrees, for example, without proscribing a specific strategy to be used by individual business owners.
“Then firms have the option either to use air conditioning or come up with some other method of climate control for their facilities,” he said, noting that some might change work hours or shorten the work day during heat waves. “It allows them to decide the most cost-effective way for them to meet the objective of reducing workplace injuries.”
Assistant Professor of Public Policy Jisung Park spoke to the Guardian about his research on the relationship between heat and student learning. Park’s studies have shown that students learn less when there are more hot school days, yet many American classrooms lack air conditioning, especially in neighborhoods of color. In one study, Park found that in years with more hot school days, students tend to do worse on state standardized exams. He also found that, on hot school days, Black and Hispanic students lost the most learning while white students were able to mitigate nearly all of the effects. In another study, Park found that central air conditioning mitigates the effects of heat by about 73%. “It’s not that we don’t understand atmospheric effects or don’t have technology to cool a room,” Park said. “So why is it that the plurality of U.S. classrooms don’t appear to have working air conditioning?”
R. Jisung Park, associate director of economic research at the UCLA Luskin Center for Innovation, spoke to KJZZ’s The Show about his research into the link between hotter temperatures and the racial achievement gap in U.S. schools. Park’s study, which measured the impact of heat exposure on reduced learning, found that the negative effect of heat is more pronounced in school districts serving underrepresented minorities. “Over time, if you experience more hot days during the school year, and especially if you go to school in an area that doesn’t appear to have adequate school facilities, for whatever reason, those small cuts do seem to add up in a way that actually ends up being measurable in your standardized achievement,” said Park, an assistant professor of public policy. “To the extent that education is such an important component of economic mobility, one would be concerned about the cumulative nature of these cuts.”
The New York Times spoke to R. Jisung Park,, associate director of economic research at the UCLA Luskin Center for Innovation, about new research showing that hotter temperatures widen the racial achievement gap in U.S. schools. Park’s study found that students performed worse on standardized tests for every additional day of 80 degrees Fahrenheit or higher, suggesting a fundamental link between heat exposure and reduced learning. While those detrimental effects were observed across 58 countries, the U.S. data revealed a surprisingly pronounced effect on Black and Hispanic students, the study found. Park, an assistant professor of public policy, said the gap seemed to reflect the fact that minority students are less likely to have air-conditioning at school and at home. Being exposed to higher temperatures throughout the school year appears to take a cumulative toll, he said. “It’s like a thousand little cuts to your ability to focus and concentrate and learn,” Park said.
Extreme heat deepens educational inequities for students around the world, according to new research by R. Jisung Park, associate director of economic research at the UCLA Luskin Center for Innovation. Just published in the journal Nature Human Behaviour, Park’s study analyzed standardized achievement data for more than 144 million 15- to 19-year-olds in 58 countries, as well as detailed weather and academic calendar information. The findings showed that the rate of learning decreases with an increase in the number of hot school days. “Temperature is a surprisingly disruptive factor for students — both for high-stakes test-taking and for learning over the longer term,” said Park, an assistant professor of public policy specializing in environmental and labor economics. The new study broadens Park’s body of research into the effect of extreme heat on learning. Previous analyses of U.S. data showed that high temperatures can diminish student performance on standardized exams. In addition, minority and low-income students who attend U.S. schools that lack air conditioning are particularly vulnerable to the negative effects of heat, the research found. The latest study measured the effects on a global scale, showing that “heat disrupts learning across a wide range of climates and levels of development,” Park said. The research underscores the importance of policies aimed at improving physical learning environments. More broadly, it demonstrates that the impact of climate change on personal development can add up over time, possibly putting a brake on national economic growth and individual economic mobility.
Assistant Professor of Public Policy R. Jisung Park was awarded a research grant by the Washington Center for Equitable Growth for a project investigating the impact of climate change on rising income inequality and declining labor market prospects in the United States. Park is one of 46 economists, postdoctoral scholars and other social scientists who received funding from the center this year to research the intersections between economic inequality and economic growth. Park’s award of $49,000 will support research into whether climate change exacerbates recent trends in economic inequality and will include recommendations for workplace adaptation and policy reforms. Growing evidence indicates that temperature stress may have significant impacts on cognitive performance, labor capacity and workplace safety, suggesting that extreme heat due to climate change may significantly reduce earnings and job quality for many low-skilled workers. Park, associate director of economic research at the UCLA Luskin Center for Innovation, will use administrative data on 11 million workplace injuries in California; injury and fatality data from the federal Office of Safety and Health Administration and the U.S. Bureau of Labor Statistics; and daily temperature variation data from the National Climatic Data Center. The Washington Center for Equitable Growth is a nonprofit research and grant-making organization dedicated to advancing policies that promote broad-based economic growth. The grant program aims to build a stronger bridge between academics and policymakers to bring relevant, accessible new research to the policymaking process.