New research uncovers surprising connection between air pollution and major illness: 'The findings here showed a positive association'
The air quality and physical health benefits of decreasing pollution have been known for decades. But scientists are now finding even more positive effects from declining pollution rates, specifically as it pertains to one major issue— dementia.
A recent international study published in Scientific Reports investigated whether greenness influences the association between particulate matter (PM) with a diameter of less than 2.5 micrometers (PM2.5) and ozone, and whether this relationship affects the disease tree that includes Alzheimer's and additional forms of dementia. Spoiler alert: the results were very positive.
"The findings here showed a positive association between annual average concentrations of PM2.5 and ozone exposure and the incidence, deaths, and DALYs of AD and other dementias," read the conclusion of the study's write-up, published on News-Medical.Net.
"A greener environment could mitigate this association, particularly at moderate-to-high greenness levels. Therefore, increasing green space worldwide would positively impact health, although the protective effects of greenness may not increase linearly at the highest levels of vegetation."
Pollution negatively impacting things like air quality and human respiratory health is kind of self-evident and wasn't ever surprising. But finding conclusive evidence of its effect on long-term neurodegenerative diseases is noteworthy and may potentially even provide a window into combating that famously hard-to-understand kind of illness.
The stakes of this finding couldn't be much higher. An American Lung Association analysis found that as many as one in three people in the U.S. is breathing unhealthy air, while the World Health Organization contends that nine out of 10 people globally breathe polluted air.
Meanwhile, in 2021, 57 million people had dementia worldwide, over 60% of whom live in low-and middle-income countries, and nearly 10 million new cases are diagnosed every year, per the WHO.
The United States government is arguably regressing in its efforts to combat pollution these days, but many other countries around the globe are rising to the challenge, slowly but surely reducing carbon pollution in the last few decades. The effects of such reductions will likely not be readily apparent for a long time, given that industrialization has coated the atmosphere in poisonous chemicals for over a century at this point.
But any progress is good progress, and the bigger (and quicker) a dent the world makes in cutting pollution, the more lives can be saved.
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Is Red Meat Bad for You? The Proof Is in the Processing
This transcript has been edited for clarity. Is red meat bad for you? On the one hand, meat makes you strong, and it's every American's God-given right to grill a steak on his barbecue during the summer. I believe this came up in a church synod at some point… But on the other hand, the WHO (World Health Organization) has declared red meat a carcinogen, with a hot dog being as bad as cigarette. Yes, that was headline when the report came out. So, how do we reconcile these opposing ideas? Part of the solution is realizing the WHO organization in question is based in France. Maybe they're still angry about the "freedom fries" thing, but actually examining the nuances of the French language will help us understand what's going on. If you don't speak French, don't worry I got you covered. Ce n'est pas si difficile de tout n'inquiétez vous pas. Vous allez voir . Sit back, grab a baguette, and let's find out how dangerous red meat really is. I'm Christopher Labos, and this is Medscape's On Second Thought . Bonjour, tout le monde! Now, meat doesn't seem like it should be a complex topic to study, but it is. Many people around the world eat animals, but we don't all eat the same animals. For example, this is a cow, often used to make hamburger and steak. And this is Tobi, God's perfect angel who gets a more elaborate birthday party than I do each year. He is my son, and I would throw myself in front of a moving car for him. By necessity, when we do medical research on meat, we are lumping together a whole lot of a different human behavior, with people eating different types of animals based on where they live. There's no real alternative, and frankly, you can't let the perfect become the enemy of the good. Most credible research will at least separate out red meat from white meat. But most people don't really know what the difference is. If you thought pork was white meat, you're wrong. You think that because of a marketing slogan. In 1987, the National Pork Board paid for the marketing campaign "Pork. The Other White Meat." They were basically trying to position pork as an alternative to chicken. People also usually think veal or deer is white meat. They think the difference between white and red meat has something to do the age of the animal, whether its free range, or the color of the meat. But it doesn't. Chefs and restaurants say all kinds of things, but the real definition is simple: Mammals are red meat, and birds are white meat. Now, there's another thing we need to explain. We have red meat, but we also have processed red meat. Processed red meat is when red meat is transformed in some way — and that doesn't mean cooking. If you just take a piece of steak and cook it on your barbecue or in the oven, that's not processed meat. Processing is doing things like salting the meat, smoking it, or curing it. Processed meat includes items like bacon, sausages, hot dogs, salami, corn beef, and smoked meat. So, when we talk about red meat and health risks, we are primarily talking about processed red meat. And the people talking about this are the International Agency for Research in Cancer (IARC). IARC is a WHO organization, and their mandate is to promote international research on cancer — particularly its cause. One of their programs is a monograph program that evaluates the evidence of the carcinogenicity of specific exposures. Here's where a knowledge of French is going to come in handy. IARC likes to look at something called the hazard, rather than the risk. In fact, every time they have a press conference, they spend about 5 minutes explaining the difference to people, which begs the question: Why not just study risk and be done with it? In English, those words seem pretty much like synonyms. And with the way most people use them, they essentially are. But in French, they are slightly different. Le risque et le hasard don't quite mean the same thing in French. To be fair, their definitions are technically different in English, as well — as those of you who read the dictionary for fun already know. A risk is the probability that something harmful will happen. A hazard is a potential source of harm. For example, a grenade is a hazardous thing to have on your desk, but the risk of it exploding is quite low… unless you pull the pin. IARC is researching hazard. They are evaluating whether something is associated with cancer, not how risky that something is. IARC categorizes everything into groups: carcinogenic to humans, probably carcinogenic, possibly carcinogenic, or not classifiable. There is technically a "not carcinogenic" group, but there's nothing in there. Well, there was one substance in there for a bit, but they removed it. Comment below if you know what that substance is. Here's a hint: You find it in yoga pants. So, IARC has never found anything that doesn't cause cancer. When they go hunting for heffalumps and woozles, they find heffalumps and woozles. To be fair, which I am under no contractual obligation to be, they are a WHO agency, and they are tasked to review substances that are of interest to world governments. As such, they are not going to review stuff that is clearly unrelated to cancer… but still. They put a lot of stuff in Group 1, the (definitely) carcinogenic group. Tamoxifen is in Group 1, and as most of you know, tamoxifen treats breast cancer. It has saved countless lives. Calling it a carcinogen sounds a bit daft, but it is associated with abnormal uterine bleeding and an increased risk of uterine cancer. And the data is pretty uncontroversial, right? Thus, IARC says, 'We are certain this association is true, therefore it goes in Group 1.' But what's the risk of tamoxifen causing uterine cancer? It's 0.3% on the absolute risk scale. It's basically zero and a heck of a lot lower than the breast cancer risk. Clearly, you should take the drug if you have ER-positive breast cancer. So, this is the problem. IARC is saying how certain they are that something is dangerous, but not how dangerous something is. Conclusive data will land a substance into Group 1: carcinogenic. Strong but not conclusive data goes into Group 2a: probably carcinogenic. If there's only some evidence, contradictory evidence, or maybe just animal data, you get sorted into Group 2b: possibly carcinogenic. And Group 3 is used when there's not much data to work off of. Generally, their system works okay. They put tobacco, asbestos, and gamma radiation in Group 1, which makes sense. But then also put stuff like birth control pills, estrogen, and tamoxifen in Group 1. Sure, there is a small increased risk of breast cancer with birth control pills if you have a family history, but it's a pretty small risk and frankly negligible for the general population — plus, it's largely outweighed by the decrease in ovarian cancer risk that comes with using birth control pills. But IARC isn't doing that type of nuanced calculation. They say, 'Estrogen causes breast cancer. The pill has estrogen. The link is proven. The pill goes into Group 1.' So, it was IARC that reviewed all the data about processed red meat and declared it a Group 1 carcinogen. Fun fact: Unprocessed red meat was only put in Group 2A because the data was less solid. For anybody grilling a steak right now, this doesn't apply to you. But not everybody agreed with IARC. The Nutritional Recommendations (NutriRECS) Consortium was a group of researchers who also reviewed the data on red meat and came to a completely different conclusion. Their analysis was motivated by two things: 1) the funding they received from the beef industry (this is why we can't have nice things), and 2) they dismissed much of the research because it comes from observational cohorts, not randomized controlled trials. In food science, randomized controlled trials are hard to conduct, because telling people what to eat is often met with "make me." Regardless, the NutriRECS Consortium conclusion was, 'Keep eating meat, as the data is uncertain because most of it is observational.' This conclusion is a bit reductionist to me, because we have a lot of observational data pointing toward health risks associated with processed red meat, and I have a hard time believing all the stuff added to processed red meat is doing us any favors. But let's take the IARC assessment at face value. They are convinced by the hazard or the hasard. But what's the risk? The cancer risk is most clear cut for colon cancer, which is pretty logical. Your lifetime risk of colon cancer is about 4%, assuming you're of general risk with no family history or genetic risk factors. It's actually 4.2% for males and 4.0% for females, according to the 2022 Cancer Statistics from the American Cancer Society. But let's say 4% for everyone — just for simplicity. The IARC report estimated that eating an extra 50 g of processed meat per day, every day, increased your risk of colorectal cancer by 18%. Take 4%, multiply it by 1.18, and you get 4.72%. So, let's say 5% if we're rounding. All this to say, if you eat hot dogs every day of your life, your risk of getting colon cancer goes up by 1 percentage point on the absolute scale. Now, on first instinct you might say, "Pfff, that's nothing. Pass the bratwurst." But 1% on the absolute scale is not trivial. That's thousands of cases per year. Millions of cases over the course of your lifetime in a country of 300 million people. It has some important public health implications. Is the risk high enough for us to stop killing and eating Bambi's mother? Hard to say. It's not negligible, but it's not astronomical either. And there are economic and environmental factors to keep in mind — issues that are often forgotten when we talk about medicine. I will stress one point, though. The IARC estimates of 1% absolute risk increase are about daily consumption of processed meat. You don't need to eat jerky every day of your life. For Medscape, I'm Dr Christopher Labos… with Tobi.
