Happy Earth Day! My toddlers celebrated with a tea party for snails and roly-polies in our backyard. I hope yours was filled with… fewer bugs.
I also hope you could pull away from the daily grind to celebrate Earth’s beauty while recognizing serious ongoing challenges, including health.
Our health is intricately and delicately tied to the planet in so many ways.
1. Nature’s healing touch
We’ve found that there is much that nature has to offer humanity:
Medicine. Roughly 9% of all plant life on Earth has been used in traditional medicine to treat and prevent disease. Plants have gifted us with important medications for the treatment of cancer (taxol, vincristine, camptothecin), pain (aspirin, morphine), infection (artemisinin), diabetes (metformin), heart disease (digoxin), and more. In 2015, scientists received the Nobel Prize for the discovery of artemisinin from wormwood for a new class of antimalarial drugs. (Go check out Nature’s Pharmacy if you’re interested in more!)
Diet. Plant-based diets rich in fruits, vegetables, and whole grains have been linked with lower risk of heart disease, stroke, cancer, and hypertension.
Sunlight. We need Vitamin D from sunlight and food for our bodies to function at their best, including bone health (maintaining adequate concentrations of calcium) and immune function support.
2. Green cities, happy minds
Green spaces, like parks and gardens, and blue spaces, like oceans, have health benefits:
Physical health. A massive meta-analysis (143 studies covering a combined sample size of >290 million people) linked green spaces to a decrease in several health outcomes, including diabetes, heart disease, and preterm birth.
Mental health. Several randomized controlled studies have found that a population’s psychological well-being can be associated with its proximity to green and blue spaces. For example, one study found that folks who spent at least 30 minutes in green spaces while living in cities had lower rates of depression.
Green spaces also have some unexpected outcomes, like reducing community violence. A randomized controlled study found a ~39% reduction in firearm violence around spaces transformed in Philadelphia.
3. Sounds that soothe (and stress) us
Listening to natural sounds, such as birdsong or ocean waves, has been found to have health benefits. Scientists think this is due to our evolution— humans attend to patterns that signal security.
One meta-analysis found water sounds had the largest effect on health and positive affective outcomes, while bird sounds had the largest effect on alleviating stress and annoyance. Both were audible >23% of the time in national parks.
Unwanted noise, like the sounds of traffic, has found the opposite.
In a systematic review, transportation noise contributed to an increased risk of heart disease, thanks to a number of hypothesized biological pathways.
4. Forests and disease
Biodiverse forests are indispensable to human health and can filter or block diseases. A recent study (2021) found increasing forest cover was associated with a decrease in disease outbreaks.
We have many recent examples of what can happen with less and less forest cover:
In the U.S., the incidence of Lyme disease has increased alongside suburban development that encroaches on forests.
The suspected first human case of the 2013-2015 Ebola outbreak was an 18-month-old boy who had been spotted playing near a hollow tree in his backyard in Guinea. The tree was infested with bats, which may have been pushed closer to the boy’s backyard due to deforestation that had destroyed 80% of the bats’ natural habitat. Research has now linked 25 Ebola outbreaks since 1976 to forest loss.
5. Mosquitos on the march
An increasingly warmer environment is causing mosquito populations to migrate to previously uncommon regions, spreading diseases.
Two species of mosquitoes responsible for carrying diseases like dengue and Zika are expanding into higher latitudes due to warming temperatures. Puerto Rico, for example, just declared a dengue health emergency.
6. Increasing heat = increasing illness
Last summer was the hottest summer ever recorded in the U.S. And it impacted health.
Asthma-associated hospital visits increased by more than 80% across New York last year due to the wildfires.
Seasonal allergy season is getting longer, and pollen counts are getting higher.
Heat-related emergency department visits (e.g., heat cramps, heat exhaustion, heat stroke) increased last summer across the U.S. compared to previous years.
But there are things we can do. As of today, CDC has a heat-illness dashboard* so people, particularly high-risk (such as pregnant women and those with asthma or heart disease), can plan their week and take action during the peak of summer.
7. Plastics and our health
In light of this year’s Earth theme, we are learning more about the impact of resources, such as microplastics, on our health.
Plastics are everywhere. We ingest and inhale them in small particles daily, which make their way into our tissues.
A very recent and concerning study linked microplastics to an increase in all-cause death, heart attack, and stroke.
Bottom line
Give me a topic, and I can link it to public health. :) In the case of Earth Day, this link isn’t hard to find: a healthy planet directly equals healthy humans. It’s that simple.
Love, YLE
Big thanks to Andrea Tamayo— an intern at YLE— who helped pull and curate a lot of these studies. She is a science journalist and master’s student at the University of California, Santa Cruz Science Communication Program. You can find more of her stories at andreactamayo.com.
*Disclaimer: I was a member of a small but mighty CDC tiger team that created this dashboard.
“Your Local Epidemiologist (YLE)” is written and founded by Dr. Katelyn Jetelina, M.P.H. Ph.D.—an epidemiologist, wife, and mom of two little girls. During the day, she is a senior scientific consultant to several organizations, including CDC. At night, she writes this newsletter. Her main goal is to “translate” the ever-evolving public health world so that people will be well-equipped to make evidence-based decisions. This newsletter is free, thanks to the generous support of fellow YLE community members. To support this effort, subscribe below:
Love this and 💯 agree.
Many physician groups are finally moving past the politics (as the kettle boils) and discussing if not outright calling for doctors to explicitly discuss climate change - not just as a public health concern for all of us, but as an actual, tangible problem for a lot of our patients’ health conditions. For example an article in the Journal of the American Board of Family Medicine:
https://www.jabfm.org/content/37/1/25
I’ll plan to keep speaking up more about this on Substack too. Thanks for this inspiration you’ve written. 🌎 happy earth day!
And thanks for the Philly green space study :)
I'm surprised you don't comment on the health benefits of electrical grounding associated with, for example, walking barefoot on the ground outside. Chinese scientist friend of mine, told me that his grandmother said that Chinese wisdom includes a saying that if you don't walk on the ground everyday you'll be sick. I found out about this when a friend of mine who had a bad case of lupus got off steroids for 2 years by sleeping in a grounded sleeping bag. Since then, I have collected a number of "Natural experiments" that point in the same direction. Actual double blend experiments show that grounding increases capillary blood flow in the extremities. Let me know if you're interested in seeing some of them.