Why do disinfectants only kill 99.9% of germs? Here’s the science
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Have you ever wondered why most disinfectants indicate they kill 99.9% or 99.99% of germs, but never promise to wipe out all of them? Perhaps the thought has crossed your mind mid-way through cleaning your kitchen or bathroom.
Surely, in a world where science is able to do all sorts of amazing things, someone would have invented a disinfectant that is 100% effective?
The answer to this conundrum requires understanding a bit of microbiology and a bit of mathematics.
What is a disinfectant?
A disinfectant is a substance used to kill or inactivate bacteria, viruses and other microbes on inanimate objects.
There are literally millions of microbes on surfaces and objects in our domestic environment. While most microbes are not harmful (and some are even good for us) a small proportion can make us sick.
Although disinfection can include physical interventions such as heat treatment or the use of UV light, typically when we think of disinfectants we are referring to the use of chemicals to kill microbes on surfaces or objects.
Chemical disinfectants often contain active ingredients such as alcohols, chlorine compounds and hydrogen peroxide which can target vital components of different microbes to kill them.
The maths of microbial elimination
In the past few years we’ve all become familiar with the concept of exponential growth in the context of the spread of COVID cases.
This is where numbers grow at an ever-accelerating rate, which can lead to an explosion in the size of something very quickly. For example, if a colony of 100 bacteria doubles every hour, in 24 hours’ time the population of bacteria would be more than 1.5 billion.
Conversely, the killing or inactivating of microbes follows a logarithmic decay pattern, which is essentially the opposite of exponential growth. Here, while the number of microbes decreases over time, the rate of death becomes slower as the number of microbes becomes smaller.
For example, if a particular disinfectant kills 90% of bacteria every minute, after one minute, only 10% of the original bacteria will remain. After the next minute, 10% of that remaining 10% (or 1% of the original amount) will remain, and so on.
Because of this logarithmic decay pattern, it’s not possible to ever claim you can kill 100% of any microbial population. You can only ever scientifically say that you are able to reduce the microbial load by a proportion of the initial population. This is why most disinfectants sold for domestic use indicate they kill 99.9% of germs.
Other products such as hand sanitisers and disinfectant wipes, which also often purport to kill 99.9% of germs, follow the same principle.
Real-world implications
As with a lot of science, things get a bit more complicated in the real world than they are in the laboratory. There are a number of other factors to consider when assessing how well a disinfectant is likely to remove microbes from a surface.
One of these factors is the size of the initial microbial population that you’re trying to get rid of. That is, the more contaminated a surface is, the harder the disinfectant needs to work to eliminate the microbes.
If for example you were to start off with only 100 microbes on a surface or object, and you removed 99.9% of these using a disinfectant, you could have a lot of confidence that you have effectively removed all the microbes from that surface or object (called sterilisation).
In contrast, if you have a large initial microbial population of hundreds of millions or billions of microbes contaminating a surface, even reducing the microbial load by 99.9% may still mean there are potentially millions of microbes remaining on the surface.
Time is is a key factor that determines how effectively microbes are killed. So exposing a highly contaminated surface to disinfectant for a longer period is one way to ensure you kill more of the microbial population.
This is why if you look closely at the labels of many common household disinfectants, they will often suggest that to disinfect you should apply the product then wait a specified time before wiping clean. So always consult the label on the product you’re using.
Other factors such as temperature, humidity and the type of surface also influence how well a disinfectant works outside the lab.
Similarly, microbes in the real world may be either more or less sensitive to disinfection than those used for testing in the lab.
Disinfectants are one part infection control
The sensible use of disinfectants plays an important role in our daily lives in reducing our exposure to pathogens (microbes that cause illness). They can therefore reduce our chances of getting sick.
The fact disinfectants can’t be shown to be 100% effective from a scientific perspective in no way detracts from their importance in infection control. But their use should always be complemented by other infection control practices, such as hand washing, to reduce the risk of infection.
Hassan Vally, Associate Professor, Epidemiology, Deakin University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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Spark – by Dr. John Ratey
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We all know that exercise is good for mental health as well as physical. So, what’s so revolutionary about this “revolutionary new science of exercise and the brain”?
A lot of it has to do with the specific neuroscience of how exercise has not only a mood-boosting effect (endorphins) and neuroprotective effect (helping to guard against cognitive decline), but also promotes neuroplasticity… e.g., the creation and strengthening of neural pathways, as well as boosting the structure of the brain in some parts such as the cerebellum.
The book also covers not just “exercise has these benefits”, but also the “how this works” of all kinds of brain benefits, including:
- against Alzheimer’s
- mitigating ADHD
- managing menopause
- dealing with addiction
…and more. And once we understand how something works, we’re far more likely to be motivated to actually do the kinds of exercises that give the specific benefits we want/need. Which is very much the important part!
In short: this book will tell you what you need to know to get you doing the exercises you need to enjoy those benefits—very much worth it!
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Superfood Energy Balls
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They are healthy, they are tasty, they are convenient! Make some of these and when you need an energizing treat at silly o’clock when you don’t have time to prepare something, here they are, full of antioxidants, vitamins and minerals, good for blood sugars too, and ready to go:
You will need
- 1 cup pitted dates
- 1 cup raw mixed nuts
- ¼ cup goji berries
- 1 tbsp cocoa powder
- 1 tsp chili flakes
Naturally, you can adjust the spice level if you like! But this is a good starter recipe.
Method
(we suggest you read everything at least once before doing anything)
1) Blend all the ingredients in a good processor to make a dough
2) Roll the dough into 1″ balls; you should have enough dough for about 16 balls. If you want them to be pretty, you can roll them in some spare dry ingredients (e.g. chopped nuts, goji berries, chili flakes, seeds of some kind, whatever you have in your kitchen that fits the bill).
3) Refrigerate for at least 1–2 hours, and serve! They can also be kept in the fridge for at least a good while—couldn’t tell you how long for sure though, because honestly, they’ve never stayed that long in the fridge without being eaten.
Enjoy!
Want to learn more?
For those interested in some of the science of what we have going on today:
- Dates vs Figs – Which is Healthier?
- Why You Should Diversify Your Nuts!
- Goji Berries: Which Benefits Do They Really Have?
- The Sugary Food That Lowers Blood Sugars
- Enjoy Bitter Foods For Your Heart & Brain
- Capsaicin’s Hot Benefits
Take care!
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What Loneliness Does To Your Brain And Body
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Spoiler: it’s nothing good (but it can be addressed!)
Not something to be ignored
Loneliness raises the risk of heart disease by 29% and the risk of stroke by 32%. It also brings about higher susceptibility to illness (flu, COVID, chronic pain, etc), as well as poor sleep quality and cognitive decline, possibly leading to dementia. Not only that, but it also promotes inflammation, and premature death (comparable to smoking).
This is because the lack of meaningful social connections activates the body’s stress response, which in turn increases paranoia, suspicion, and social withdrawal—which makes it harder to seek the social interaction needed to alleviate it.
On a neurological level, cortisol levels become imbalanced, and a faltering dopamine response leads to impulsive behaviors (e.g., drinking, gambling) to try to make up for it. Decreased serotonin, oxytocin, and natural opioids reduce feelings of happiness and negate pain relief.
As for combatting it, the first-line remedy is the obvious one: connecting with others improves emotional and physical wellbeing. However, it is recommended to aim for deep, meaningful connections that make you happy rather than just socializing for its own sake. It’s perfectly possible to be lonely in a crowd, after all.
A second-line remedy is to simply mitigate the harm by means of such things as art therapy and time in nature—they can’t completely replace human connection, but they can at least improve the neurophysiological situation (which in turn, might be enough of a stop-gap solution to enable a return to human connection).
For more on all of this, enjoy:
Click Here If The Embedded Video Doesn’t Load Automatically!
Want to learn more?
You might also like to read:
How To Beat Loneliness & Isolation
Take care!
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Twenty-One, No Wait, Twenty Tweaks For Better Health
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Dr. Greger’s 21 Tweaks… We say 20, though!
We’ve talked before about Dr. Greger’s Daily Dozen (12 things he advises that we make sure to eat each day, to enjoy healthy longevity), but much less-talked-about are his “21 Tweaks”…
They are, in short, a collection of little adjustments one can make for better health. Some of them are also nutritional, but many are more like lifestyle tweaks. Let’s do a rundown:
At each meal:
- Preload with water
- Preload with “negative calorie” foods (especially: greens)
- Incorporate vinegar (1-2 tbsp in a glass of water will slow your blood sugar increase)
- Enjoy undistracted meals
- Follow the 20-minute rule (enjoy your meal over the course of at least 20 minutes)
Get your daily doses:
- Black cumin ¼ tsp
- Garlic powder ¼ tsp
- Ground ginger (1 tsp) or cayenne pepper (½ tsp)
- Nutritional yeast (2 tsp)
- Cumin (½ tsp)
- Green tea (3 cups)
Every day:
- Stay hydrated
- Deflour your diet
- Front-load your calories (this means implementing the “king, prince, pauper” rule—try to make your breakfast the largest meal of your day, followed my a medium lunch, and a small evening meal)
- Time-restrict your eating (eat your meals within, for example, an 8-hour window, and fast the rest of the time)
- Optimize exercise timing (before breakfast is best for most people, unless you are diabetic)
- Weigh yourself twice a day (doing this when you get up and when you go to bed results in much better long-term weight management than weighing only once per day)
- Complete your implementation intentions (this sounds a little wishy-washy, but it’s about building a set of “if this, then that” principles, and then living by them. An example could be directly physical health-related such as “if there is a choice of stairs or elevator, I will take the stairs”, or could be more about holistic good-living, such as “if someone asks me for help, I will try to oblige them so far as I reasonably can”)
Every night:
- Fast after 7pm
- Get sufficient sleep (7–9 hours is best. As we get older, we tend more towards the lower end of that, but try get at least those 7 hours!)
Experiment with Mild Trendelenburg(better yet, skip this one)*
*This involves a 6º elevation of the bed, at the foot end. Dr. Greger advises that this should only be undertaken after consulting your doctor, though, as a lot of health conditions can contraindicate it. We at 10almonds couldn’t find any evidence to support this practice, and numerous warnings against it, so we’re going to go ahead and say we think this one’s skippable.
Again, we do try to bring you the best evidence-based stuff here at 10almonds, and we’re not going to recommend something just because of who suggested it
As for the rest, you don’t have to do them all! And you may have noticed there was a little overlap in some of them. But, we consider them a fine menu of healthy life hacks from which to pick and choose!
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The Most Anti Aging Exercise
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We’ve referenced this (excellent) video before, but never actually put it under the spotlight in one of these features, so here we go!
Deep squats
It’s about deep squats, also called Slav squats, Asian squats, sitting squats, resting squats, or various other names. However, fear not; you don’t need to be Slavic or Asian to do it; you just need to practice.
As for why this is called “anti-aging”, by the way, it’s because being able to get up off the ground is one of the main tests of age-related mobility decline, and if you can deep-squat comfortably, then you can do that easily. And so long as you continue being able to deep-squat comfortably, you’ll continue to be able to get up off the ground easily too, because you have the strength in the right muscles, as well as the suppleness, comfort with range of motion, and balance (those stabilizing muscles are used constantly in a deep squat, whereas Western lifestyle sitting leaves those muscles very neglected and thus atrophied).
Epidemiological note: chairs, couches, and assorted modern conveniences reduce the need for squatting in daily life, leading to stiffness in joints, muscles, tendons, and ligaments. Many adults in developed countries struggle with deep squats due to lack of use, not aging. Which is a problem, because a lack of full range of motion in joints causes wear and tear, leading to chronic pain and degenerative joint diseases. People in countries where squatting is a common resting position have lower incidences of osteoarthritis, for example—contrary to what some might expect, squatting does not harm joints but rather protects them from arthritis and knee pain. Strengthening leg muscles through squatting can alleviate knee pain, whereas knee pain is often worsened by inactivity.
Notwithstanding the thumbnail, which is showing an interim position, one’s feet should be flat on the ground, by the way, and one’s butt should be nearby, just a few inches off the ground (in other words, the position that we see her in for most of this video).
Troubleshooting: if you’re accustomed to sitting in chairs a lot, then this may be uncomfortable at first. Zuzka advises us to go gently, and/but gradually increase our range of motion and (equally importantly) duration in the resting position.
You can use a wall or doorway to partially support you, at first, if you struggle with mobility or balance. Just try to gradually use it less, until you’re comfortable deep-squatting with no support.
Since this is not an intrinsically very exciting exercise, once you build up the duration for which you’re comfortable deep-squatting, it can be good to get in the habit of “sitting” this way (i.e. deep squatting, still butt-off-the-floor, but doing the job of sitting) while doing other things such as working (if you have an appropriate work set-up for that*), reading, or watching TV.
*this is probably easiest with a laptop placed on an object/surface of appropriate height, such as a coffee table or such. As a bonus, having your hands in front of you while working will also bring your center of gravity forwards a bit, making the position easier and more comfortable to maintain. This writer (hi, it’s me) prefers her standing desk for work in general, with a nice ergonomic keyboard and all that, but if using a laptop from time to time, then squatting is a very good option.
In terms of working up duration, if you can only manage seconds to start with, that’s fine. Just do a few more seconds each time, until it’s 30, 60, 120, and so on until it’s 5 minutes, 10, 15, and so on.
You can even start that habit-forming while you’re still in the “seconds at a time” stage! You can deep-squat just for some seconds while you:
- pick up something from the floor
- check on something in the oven
- get something out of the bottom of the fridge
…etc!
For more on all this, plus many visual demonstrations including interim exercises to get you there if it’s difficult for you at first, enjoy:
Click Here If The Embedded Video Doesn’t Load Automatically!
Want to learn more?
You might also like to read:
Mobility For Now & For Later: Train For The Marathon That Is Your Life!
Take care!
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7 Minutes, 30 Days, Honest Review: How Does The 7-Minute Workout Stack Up?
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For those who don’t like exercising, “the 7-minute workout” (developed by exercise scientists Chris Jordan and Bret Klika) has a lot of allure. After all, it’s just 7 minutes and then you’re done! But how well does it stand up, outside of the lab?
Down-to-Earth
Business Insider’s Kelly Reilly is not a health guru, and here he reviews the workout for us, so that we can get a real view of what it’s really like in the real world. What does he want us to know?
- It’s basically an optimized kind of circuit training, and can be done with no equipment aside from a floor, a wall, and a chair
- It’s one exercise for 30 seconds, then 10 seconds rest, then onto the next exercise
- He found it a lot easier to find the motivation to do this, than go to the gym. After all “it’s just 7 minutes” is less offputting than getting in the car, driving someplace, using public facilities, driving back, etc. Instead, it’s just him in the comfort of his home
- The exercise did make him sweat and felt like a “real” workout in that regard
- He didn’t like missing out on training his biceps, though, since there are no pulling movements
- He lost a little weight over the course of the month, though that wasn’t his main goal (and indeed, he was not eating healthily)
- He did feel better each day after working out, and at the end of the month, he enjoyed feeling self-confident in a tux that now fitted him better than it did before
For more details, his own words, and down-to-earth visuals of what this looked like for him, enjoy:
Click Here If The Embedded Video Doesn’t Load Automatically!
Further reading
Want to know more? Check out…
- How To Do HIIT (Without Wrecking Your Body)
- HIIT, But Make It HIRT ← this is about high-intensity resistance training!
Take care!
Don’t Forget…
Did you arrive here from our newsletter? Don’t forget to return to the email to continue learning!
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