Spotlight on Research Into Heat-Triggered Injuries

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.


 

High Temperatures Increase Workers’ Injury Risk, Whether They’re Outdoors or Inside The finding reflects another consequence of climate change, according to new study led by R. Jisung Park of UCLA Luskin Public Policy

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.”

 

Heat Exacerbates Educational Divide, Park Finds

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?”

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Park on Cumulative Effect of Heat on Learning

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.”

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Park on New Research on Heat, Learning and the Racial Gap

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.

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New Research Shows Global Impact of Extreme Heat on Learning

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.


 

Park Awarded Equitable Growth Research Grant

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.


Park on California as Ground Zero for Climate Disaster

Assistant Professor of Public Policy R. Jisung Park spoke to the New York Times for a story about the engineering and land management innovations that led to California’s tremendous growth but also left it vulnerable to climate disaster. For generations, the state has moved vast quantities of water and suppressed wildfires to transform its arid and mountainous landscape into the “richest, most populous and bounteous place in the nation,” the article noted. While these accomplishments reflect the optimism that defines California, Park said, they were not designed to accommodate the increasingly harsh extremes of climate change. “The shocks are outside the range, in many cases, of historical experience,” he said. Park also noted that California’s engineered landscapes are not the only factor behind its high-impact disasters. The state’s size, geographic diversity and large population also expose it to an unusually wide range of extreme climate events.

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Park on the Visceral Impacts of Climate Change

Assistant Professor of Public Policy R. Jisung Park was featured in a Sustainable LA Grand Challenges Spotlight article discussing his research on the links between heat and student performance. Park analyzed New York City standardized test scores over 20 years and found that students taking an exam on a 90-degree day do a “10-15% of a standard deviation worse than they would have otherwise.” He explained that the impacts of heat are disproportionately high for underrepresented minorities, who are significantly less likely to have air conditioning at school and home. “I would hope that this kind of research can at least help us make more visceral the impacts of climate change and make it less of a ‘other people over there 100 years from now’ problem and more of an ‘all of us today’ problem,” Park said. He stressed the importance of developing a short-term policy portfolio in addition to a long-term carbon mitigation plan.

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Park on Unintended Consequences of Development Restrictions

Assistant Professor of Public Policy Jisung Park spoke to the New York Times about potential unintended consequences of climate change development restrictions on poorer communities. A new study found that many Americans support aggressive government regulation to fight the effects of climate change, including mandatory building codes in risky areas and bans on building in flood- or fire-prone areas. While development restrictions could reduce disasters in the future, Park noted that they could also hurt low-income and minority families who can’t afford to live elsewhere. If local governments follow public opinion and impose new restrictions on development, it’s important that they consider the effects of those changes on poorer communities, including communities of color, Park said. He suggested that governments could make it more expensive to live in vulnerable neighborhoods, but subsidize low-income residents who want to move. “Doing both is certainly possible,” he said.

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