Forget 98.6°F. Humans Are Cooling off — Here’s Why
By Kristen Fischer
The "normal" body temperature of 98.6°F (37°C) is actually not so normal. New research finds the average human body temperature of Americans has dropped.
"What everybody grew up learning, which is that our normal temperature is 98.6, is wrong," said Dr. Julie Parsonnet, a professor of medicine as well as health research and policy at Stanford University School of Medicine.
The 98.6°F standard was established by a German doctor in 1851. Recent studies have indicated that's too high; research on 35,000 British people found their average was 97.9°F.
Parsonnet's study published this week in eLife. It found that temperature changes since 1851 reflect a historical pattern instead of an error. They contend the decrease is the result of environmental changes over the past 200 years that have affected human physiology.
Parsonnet looked at data from 1862 through 1930, 1971 through 1975, and 2007 through 2017. It included 677,423 temperature measurements.
The body temperature of men born in the 2000s is 1.06°F degrees lower, on average, than men born in the early 1800s. Women have temps about 0.58°F lower than those born in the 1890s. That means body temperatures declined 0.05°F every decade.
Parsonnet's team also found a decline in temperature since the 1960s, not just since the Civil War.
Body temperature is complicated, Parsonnet says. It can vary not just from person to person but at different times of day and at different ages.
It can be almost half a degree higher in the afternoon than morning. It's much lower in older adults. Your weight and height as well as hot or humid weather can also affect it, Parsonnet says.
In her experience, Parsonnet says at least 75 percent of normal temperatures are below 98.6°F.
"Even in younger adults at the end of the day, when temperatures are at their highest, the temperature still doesn't get up to 98.6," she said. "In the elderly, it would be quite unusual to have a temperature as high as 98.6."
"The threshold for fever is generally held as 1°C above normal," said Dr. Bradley Uren, assistant professor of emergency medicine at Michigan Medicine. "A fever is generally held as 38°C, or 100.4°F."
"It is rare to see a patient at exactly 98.6," he noted. "A temperature is just one piece of information that physicians must and do consider in determining a course of treatment for an individual."
Even though our temperatures can fluctuate, doctors still know what's generally normal. They also know to look for variations in temperature, which can indicate a medical condition, Uren says.
"Physicians must take into account the entirety of a patient's condition in determining if a temperature, either higher or lower, or even within the normal range, is significant," Uren said.
"For example, patients may be treated for infection even with a normal temperature if the other historical and physical findings, and the patient's overall condition, is consistent with infection," he said.
Dr. Amy Mullins, medical director of quality improvement for the American Academy of Family Physicians, notes that the study won't change how patients or doctors should define fevers.
Why Temps Are Falling
It's possible that some of these changes may be because thermometers provide more accurate readings, Parsonnet noted in her study.
However, that doesn't explain all of it. Temperatures declined over time even when her team controlled for different devices.
Susan Yeargin, Ph.D., associate professor of exercise science at University of South Carolina, has tested all types of temperature devices in diagnosing hyper- and hypothermia. They were inaccurate compared to the rectal temperature.
"Each person's unique normothermic body temperature should be considered by healthcare providers. Certain medications can influence a person's regular 'set point' temperature, and obviously hot and cold outdoor temperatures can affect a person's body temperature over time," Yeargin said.
"When healthcare providers give advice to individuals about these medications and environments, their unique normothermic body temperature should be considered," she said.
According to Parsonnet, other reasons for the decline in body temperature over time could be that we're also using less energy and have a lower metabolic rate than in the past.
The reduction may be due to a population-wide decline in inflammation. Generally, inflammation increases our metabolism and raises temperature.
Because of improvements in public health, this could be why inflammation has decreased. The ambient temperatures we live in, thanks to heating and air conditioning, could be factors in lower metabolic rates.
"I think it's most likely because we have much less inflammation in our bodies now than we did when the standard was developed in the mid-19th century," Parsonnet said.
"We have less inflammation because we have far fewer chronic infectious diseases like tuberculosis and periodontal disease, far less recurrent infection, shifts in our microbiomes, and we also have learned how to combat inflammation directly through better diets, and also with things like nonsteroidal drugs and statins," she explained.
In general, humans are physiologically different than we were in the past, Parsonnet says.
Reposted with permission from Healthline.
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Natural gas is a versatile fossil fuel that accounts for about a third of U.S. energy use. Although it produces fewer greenhouse gas emissions and other pollutants than coal or oil, natural gas is a major contributor to climate change, an urgent global problem. Reducing emissions from the natural gas system is especially challenging because natural gas is used roughly equally for electricity, heating, and industrial applications.
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What RNG Is and Why it Matters<p>Most equipment that uses energy can only use a single kind of fuel, but the fuel might come from different resources. For example, you can't charge your computer with gasoline, but it can run on electricity generated from coal, natural gas or solar power.</p><p>Natural gas is almost pure methane, <a href="https://www.eia.gov/energyexplained/natural-gas/" target="_blank">currently sourced</a> from raw, fossil natural gas produced from <a href="https://www.eia.gov/energyexplained/natural-gas/where-our-natural-gas-comes-from.php" target="_blank">deposits deep underground</a>. But methane could come from renewable resources, too.</p><p><span></span>Two main methane sources could be used to make RNG. First is <a href="https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-and-sinks" target="_blank">biogenic methane</a>, produced by bacteria that digest organic materials in manure, landfills and wastewater. Wastewater treatment plants, landfills and dairy farms have captured and used biogenic methane as an energy resource for <a href="http://emilygrubert.org/wp-content/uploads/2019/02/eia_860_2017_map.html" target="_blank">decades</a>, in a form usually called <a href="https://www.eia.gov/energyexplained/biomass/landfill-gas-and-biogas.php" target="_blank">biogas</a>.</p><p>Some biogenic methane is generated naturally when organic materials break down without oxygen. Burning it for energy can be beneficial for the climate if doing so prevents methane from escaping to the atmosphere.</p>
Renewable Isn’t Always Sustainable<p>If RNG could be a renewable replacement for fossil natural gas, why not move ahead? Consumers have shown that they are <a href="https://www.nrel.gov/analysis/green-power.html" target="_blank">willing to buy renewable electricity</a>, so we might expect similar enthusiasm for RNG.</p><p>The key issue is that methane isn't just a fuel – it's also a <a href="https://www.eia.gov/environment/emissions/ghg_report/ghg_overview.php" target="_blank">potent greenhouse gas</a> that contributes to climate change. Any methane that is manufactured intentionally, whether from biogenic or other sources, will contribute to climate change if it enters the atmosphere.</p><p>And <a href="http://doi.org/10.1126/science.aar7204" target="_blank">releases</a> <a href="https://doi.org/10.1016/j.wasman.2019.07.029" target="_blank">will happen</a>, from newly built production systems and <a href="https://theconversation.com/why-methane-emissions-matter-to-climate-change-5-questions-answered-122684" target="_blank">existing, leaky transportation and user infrastructure</a>. For example, the moment you smell gas before the pilot light on a stove lights the ring? That's methane leakage, and it contributes to climate change.</p><p>To be clear, RNG is almost certainly better for the climate than fossil natural gas because byproducts of burning RNG won't contribute to climate change. But doing somewhat better than existing systems is no longer enough to respond to the <a href="https://doi.org/10.1038/nclimate2923" target="_blank">urgency</a> of climate change. The world's <a href="https://www.ipcc.ch/sr15/chapter/spm/" target="_blank">primary international body on climate change</a> suggests we need to decarbonize by 2030 to mitigate the worst effects of climate change.</p>
Scant Climate Benefits<p><a href="https://iopscience.iop.org/article/10.1088/1748-9326/ab9335/meta" target="_blank">My recent research</a> suggests that for a system large enough to displace a lot of fossil natural gas, RNG is probably not as good for the climate as <a href="https://investor.southerncompany.com/information-for-investors/latest-news/latest-news-releases/press-release-details/2020/Southern-Company-Gas-grows-leadership-team-to-focus-on-climate-action-innovation-and-renewable-natural-gas-strategy/default.aspx" target="_blank">is publicly claimed</a>. Although RNG has lower climate impact than its fossil counterpart, likely high demand and methane leakage mean that it probably will contribute to climate change. In contrast, renewable sources such as wind and solar energy do not <a href="https://www.eia.gov/environment/emissions/carbon/" target="_blank">emit climate pollution directly</a>.</p><p>What's more, creating a large RNG system would require building mostly new production infrastructure, since RNG comes from different sources than fossil natural gas. Such investments are both long-term commitments and opportunity costs. They would devote money, political will and infrastructure investments to RNG instead of alternatives that could achieve a zero greenhouse gas emission goal.</p><p>When climate change first <a href="https://www.nytimes.com/1988/06/24/us/global-warming-has-begun-expert-tells-senate.html" target="_blank">broke into the political conversation</a> in the late 1980s, investing in long-lived systems with low but non-zero greenhouse gas emissions was still compatible with aggressive climate goals. Now, zero greenhouse gas emissions is the target, and my research suggests that large deployments of RNG likely won't meet that goal.</p>
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By Charli Shield
When an elephant dies in the wild, it's not uncommon to later find its bones scattered throughout the surrounding landscape.
Elephant Burial Grounds<p>Highly social creatures that form deep familial bonds, elephants have long been observed gathering at the site where a peer or family member has died — often spending hours, even days, quietly investigating the bodies or the bones of other dead elephants.</p><p>Although the popular idea that dying elephants are instinctively drawn to special communal graves — so-called "elephant graveyards" — is a myth, their tendency to go out of their way to visit the bones and tusks of the deceased isn't unlike human rituals at graveyards, says animal psychologist Karen McComb.</p><p>"They spend a lot of time touching and smelling skulls and ivory, placing the soles of their feet gently on top of them, and also lifting them up with their trunks," McComb, who's been studying African elephants for 25 years in Kenya's Amboseli National Park, told DW.</p><p>The most striking part of watching an elephant experience loss, Poole recalls, is the quietude. She still remembers one of the first elephant deaths she witnessed; a mother who birthed a stillborn calf. That elephant stayed with its baby for two days, trying to lift it and defending it from vultures and hyenas.</p><p>"I was so struck by the expression on her face and her body. She looked so dejected. It was really like, 'Oh God, these animals grieve…'. It was just so different," Poole told DW. </p>
Witnessing Emotions in Animals<p>Not all scientists are comfortable concluding that elephants grieve. Among the more than 30 reports of elephant reactions to death that Wittemyer co-reviewed in <a href="https://link.springer.com/article/10.1007/s10329-019-00766-5" target="_blank">a study published in November 2019</a> were accounts of "enormous variation and nuance" he says. "It can be incredibly involved and intricate for extended periods or can be relatively cursory checks."</p><p>In Wittemyer's own experience, it can be difficult not to attribute some kind of emotional experience to the more involved interactions between elephants and their dead.</p><p>He shares the story of an "extraordinary event" involving the death of a 55 year-old matriarch in Kenya in a protected area that happened to be near his place of work. She was visited by multiple unrelated families while she was dying, including another matriarch that exerted such enormous effort attempting to lift her to her feet that she broke her tusk, which Wittemyer says, is "like breaking a tooth." </p><p><span></span>"It was a remarkable example of this heightened emotional state, it was very clearly a very stressful interaction," he says.</p>
A Different Sensory World<p>One factor that limits our ability to fully grasp the way elephants process and respond to loss is our markedly different sensory experiences of the world.</p><p>An elephant's world is fundamentally olfactory — based on smell. Ours is visual. Previous <a href="https://pubmed.ncbi.nlm.nih.gov/25053675/" target="_blank">research</a> has shown elephants possess the most scent receptors of any mammal, and can <a href="https://pubmed.ncbi.nlm.nih.gov/17949977/" target="_blank">use smell</a> to discern the difference between different human tribes from the same local area.</p><p>That could explain why elephants exhibit such interest in sniffing the bones and tusks of others, as a <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1617198/" target="_blank">2005 study</a> from McCombs highlighted. When presented with the skulls and ivory of long-dead elephants and those from other large herbivores, including rhino and buffalo, McCombs and her team found elephants approached and were specifically attracted to the remains of their own species. </p><p>Without access to the smells an elephant picks up on, Wittemyer says "an enormous amount of stuff" could be missed by humans when studying these behaviors.</p>
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