Climate change to make outdoor work more dangerous

Today's agriculture workers face 21 days of heat that exceed safety standards. That number will double by 2050.

(Photo: Guillermo Arias/AFP via Getty Images)
  • According to a recent study, the number of days agricultural works will spend in sweltering, unsafe conditions will double by 2050 and triple by 2100.
  • These workers already face significant health risks due to compounding circumstances such as poverty, migrant status, and a lack of access to health care.
  • Climate change will make many the United States' most fatal occupations more dangerous, but no less essential.

    • Discussions of the climate crisis tend to view future consequences on a global scale. Hot and more acidic oceans will lead to coral death and species die-offs. Increased growing seasons and less snowpack will stress watersheds. Acts of God (or Mother Nature) such as droughts, hurricanes, and forest fires will become alarmingly frequent parts of our annual routines.

      Even when we turn our attention to the human toll, our focus can be statistically stoic. Effects like large-scale human migration, interstate competition for resources, and degradation of habitable land are terrifying, but from our contemporary vantage, they too easily read like local news from several states over. Horrible but distant.

      But a recent study in Environmental Research Letters has narrowed the focus. It shows that an increase in global temperatures by 2°C will affect everyone, neighbors and friends, whose job takes them outside.

      Turning up the heat index

      Three maps showing the maximum daily heat index, in Fahrenheit, for the top 5% of the hottest days in the growing season.

      Photo: Michelle Tigchelaar et al./Environmental Research Letters

      The study's authors spotlighted how the climate crisis will transform agricultural work. They chose agriculture not only because its workers are essential, but because few studies had looked at the men and women who support this economic cornerstone.

      "Studies of climate change and agriculture have traditionally focused on crop yield projections, especially staple crops like corn and wheat," Michelle Tigchelaar, the study's lead author and a postdoctoral researcher at Stanford University, said in a release. "This study asks what global warming means for the health of agricultural workers picking fruits and vegetables."

      The researchers obtained employment data from the Bureau of Labor Statistics' (BLS) Quarterly Census of Employment and Wages program and used it to determine the number of workers in the America's agricultural counties during the growing season (May through September).

      They then compared that data to models of climate change, using "business-as-usual scenarios" in which carbon emissions neither increase nor decrease drastically in the coming years. According to these conservative models, global temperatures are projected to increase by 2°C (~36°F) by 2050 and 4°C (~39°F) by 2100.

      Finally, the researchers used the heat index—a single value that combines temperature with humidity—to determine risky work conditions. According to OSHA guidelines, a heat index of 91–103° represents a moderate risk and requires precautionary measures. Anything higher represents a serious workplace hazard, requiring additional precautionary measures by employers.

      Their use of the heat index is critical as climate change won't only increase the planet's temperature. It will increase global humidity, too.

      It's the humidity

      Typically, our bodies perspire to cool down. On dry summer days, sweat evaporates from our skin to transfer our metabolic heat into the air around us. But when humidity rises, sweat evaporates much slower as the surrounding air is thick with water.

      Because of this, humid days don't just feel hotter. According to our bodies, humid days are hotter. We experience an 88°F day with 85 percent humidity as though it were a stifling 110°F.

      Exposure to such heat can cause illnesses such as sunburn, heat cramps, and heat exhaustion. If a person's temperature reaches 103°F or higher, they may suffer from heatstroke which can result in headaches, nausea, fatigue, confusion, loss of consciousness, and even death.

      Chronic overheating has been correlated with stress-related heart, kidney, and liver damage, though studies have not shown conclusive causation.

      This makes a hotter, more humid planet more dangerous for outdoor workers.

      Today, the average U.S. agricultural worker experiences 21 days per growing season when the daily heat index exceeds safety standards. Even then, agricultural workers are four times more likely to suffer heat-related illnesses than non-agricultural workers and suffer four heat-related deaths per one million workers per year, a rate 20 times higher than other U.S. civilian workers.

      When global temperatures rise by two degrees, according to the study, the average agricultural worker will face 39 days of heat that exceed safety standards. At four degrees warming, that number grows to 62 days. Their data also show that heatwaves—defined as a three-or-more-day stretches of extreme heat—will become five times as frequent by 2050.

      "The climate science community has long been pointing to the global south, the developing countries, as places that will be disproportionately affected by climate change," David Battisti, co-author and a UW professor of atmospheric sciences, said in the same release. "This shows that you don't have to go to the global south to find people who will get hurt with even modest amounts of global warming -- you just have to look in our own backyard."

      It's worth noting that those numbers are averages, and agricultural workers in different locations will encounter drastically different conditions.

      For example, the study's data show counties in Washington state remaining on the cooler side of the median. Meanwhile, workers in Imperial, California already contend with 105 days that exceed safety standards. By the year 2100, that number will jump to 136—nearly the entire growing season!

      The costs will be global

      The heat won't just affect agricultural workers; billions of people of people worldwide live without air conditioning and other cooling amenities.

      (Photo: Arindam Dey/AFP via Getty Images)

      Heat-related illnesses are a concern for all outdoor workers, but agriculture workers are particularly vulnerable as they typically lack health insurance and have low incomes.

      The study authors propose strategies to help offset forthcoming heat hazards. They recommend reducing the pace of work; adopting thinner, breathable clothes; and taking longer breaks in cooled and sheltered areas.

      But these recommendations come with trade-offs. Breathable clothing is not an option when personal protective gear is necessary to protect workers from dust, pesticides, and UV radiation, and the slower pace would hurt productivity and, as a consequence, worker's already low pay.

      According to Patrick Behrer, an environmental and developmental economist and Harvard Ph.D. candidate in the Graduate School of Arts and Scienceswho was not involved in the research, the relationship between heat and pay will take its toll on workers:

      "Relative to the other damages of climate change, the impact of any given hot day is small, both in absolute and relative terms; some of our other work suggests that just one additional hot day removes a fraction of a percent of your annual take-home pay. When you start talking about going from eight extremely hot days to 50 extremely hot days, then that adds up very quickly. It also adds up very quickly when you're taking a fraction of a percent of pay away from large parts of the United States."

      Of the U.S.'s most fatal occupations, eight of the nine are either performed outdoors or in environments that make heat-regulation difficult to manage, such as iron and steel-working. Without proper preparation, it isn't difficult to imagine how fatigue, confusion, and other heat-related symptoms may exacerbate dangerous conditions for these essential workers.

      And it is not only workers. By one study's estimate, the billions of people worldwide who can't afford air conditioning will be at risk—any one of which may be a friend, neighbor, or essential member of society much closer than the next state over.

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      New research establishes an unexpected connection.

      Reactive oxygen species (ROS) accumulate in the gut of sleep-deprived fruit flies, one (left), seven (center) and ten (right) days without sleep.

      Image source: Vaccaro et al, 2020/Harvard Medical School
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      • When the buildup is neutralized, a normal lifespan is restored.

      We don't have to tell you what it feels like when you don't get enough sleep. A night or two of that can be miserable; long-term sleeplessness is out-and-out debilitating. Though we know from personal experience that we need sleep — our cognitive, metabolic, cardiovascular, and immune functioning depend on it — a lack of it does more than just make you feel like you want to die. It can actually kill you, according to study of rats published in 1989. But why?

      A new study answers that question, and in an unexpected way. It appears that the sleeplessness/death connection has nothing to do with the brain or nervous system as many have assumed — it happens in your gut. Equally amazing, the study's authors were able to reverse the ill effects with antioxidants.

      The study, from researchers at Harvard Medical School (HMS), is published in the journal Cell.

      An unexpected culprit

      The new research examines the mechanisms at play in sleep-deprived fruit flies and in mice — long-term sleep-deprivation experiments with humans are considered ethically iffy.

      What the scientists found is that death from sleep deprivation is always preceded by a buildup of Reactive Oxygen Species (ROS) in the gut. These are not, as their name implies, living organisms. ROS are reactive molecules that are part of the immune system's response to invading microbes, and recent research suggests they're paradoxically key players in normal cell signal transduction and cell cycling as well. However, having an excess of ROS leads to oxidative stress, which is linked to "macromolecular damage and is implicated in various disease states such as atherosclerosis, diabetes, cancer, neurodegeneration, and aging." To prevent this, cellular defenses typically maintain a balance between ROS production and removal.

      "We took an unbiased approach and searched throughout the body for indicators of damage from sleep deprivation," says senior study author Dragana Rogulja, admitting, "We were surprised to find it was the gut that plays a key role in causing death." The accumulation occurred in both sleep-deprived fruit flies and mice.

      "Even more surprising," Rogulja recalls, "we found that premature death could be prevented. Each morning, we would all gather around to look at the flies, with disbelief to be honest. What we saw is that every time we could neutralize ROS in the gut, we could rescue the flies." Fruit flies given any of 11 antioxidant compounds — including melatonin, lipoic acid and NAD — that neutralize ROS buildups remained active and lived a normal length of time in spite of sleep deprivation. (The researchers note that these antioxidants did not extend the lifespans of non-sleep deprived control subjects.)

      fly with thought bubble that says "What? I'm awake!"

      Image source: Tomasz Klejdysz/Shutterstock/Big Think

      The experiments

      The study's tests were managed by co-first authors Alexandra Vaccaro and Yosef Kaplan Dor, both research fellows at HMS.

      You may wonder how you compel a fruit fly to sleep, or for that matter, how you keep one awake. The researchers ascertained that fruit flies doze off in response to being shaken, and thus were the control subjects induced to snooze in their individual, warmed tubes. Each subject occupied its own 29 °C (84F) tube.

      For their sleepless cohort, fruit flies were genetically manipulated to express a heat-sensitive protein in specific neurons. These neurons are known to suppress sleep, and did so — the fruit flies' activity levels, or lack thereof, were tracked using infrared beams.

      Starting at Day 10 of sleep deprivation, fruit flies began dying, with all of them dead by Day 20. Control flies lived up to 40 days.

      The scientists sought out markers that would indicate cell damage in their sleepless subjects. They saw no difference in brain tissue and elsewhere between the well-rested and sleep-deprived fruit flies, with the exception of one fruit fly.

      However, in the guts of sleep-deprived fruit flies was a massive accumulation of ROS, which peaked around Day 10. Says Vaccaro, "We found that sleep-deprived flies were dying at the same pace, every time, and when we looked at markers of cell damage and death, the one tissue that really stood out was the gut." She adds, "I remember when we did the first experiment, you could immediately tell under the microscope that there was a striking difference. That almost never happens in lab research."

      The experiments were repeated with mice who were gently kept awake for five days. Again, ROS built up over time in their small and large intestines but nowhere else.

      As noted above, the administering of antioxidants alleviated the effect of the ROS buildup. In addition, flies that were modified to overproduce gut antioxidant enzymes were found to be immune to the damaging effects of sleep deprivation.

      The research leaves some important questions unanswered. Says Kaplan Dor, "We still don't know why sleep loss causes ROS accumulation in the gut, and why this is lethal." He hypothesizes, "Sleep deprivation could directly affect the gut, but the trigger may also originate in the brain. Similarly, death could be due to damage in the gut or because high levels of ROS have systemic effects, or some combination of these."

      The HMS researchers are now investigating the chemical pathways by which sleep-deprivation triggers the ROS buildup, and the means by which the ROS wreak cell havoc.

      "We need to understand the biology of how sleep deprivation damages the body so that we can find ways to prevent this harm," says Rogulja.

      Referring to the value of this study to humans, she notes,"So many of us are chronically sleep deprived. Even if we know staying up late every night is bad, we still do it. We believe we've identified a central issue that, when eliminated, allows for survival without sleep, at least in fruit flies."

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