Today’s news coverage reports potentially unsafe levels of “forever chemicals” detected in drinking water supplies around Australia. These include human-made chemicals: perfluorooctane sulfonate (known as PFOS) and perflurooctanic acid (PFOA). They are classed under the broader category of per- and polyfluoroalkyl substances or PFAS chemicals.

The contaminants found in our drinking water are the same ones United States authorities warn can cause cancer over a long period of time, with reports warning there is “no safe level of exposure”.

In April, the US Environmental Protection Agency (USEPA) sent shock waves through the water industry around the world when it announced stricter advice on safe levels of PFOS/PFOA in drinking water. This reduced limits considered safe in supplies to zero and gave the water industry five years to meet legally enforceable limits of 4 parts per trillion.

So, should the same limits be enforced here in Australia? And how worried should we be that the drinking in many parts of Australia would fail the new US standards?

What are the health risks?

Medical knowledge about the human health effects of PFOS/PFOA is still emerging. An important factor is the bioaccumulation of these chemicals in different organs in the body over time.

Increased exposure of people to these chemicals has been associated with several adverse health effects. These include higher cholesterol, lower birth weights, modified immune responses, kidney and testicular cancer.

It has been very difficult to accurately track and measure effects of different levels of PFAS exposure on people. People may be exposed to PFAS chemicals in their everyday life through waterproofing of clothes, non-stick cookware coatings or through food and drinking water. PFAS can also be in pesticides, paints and cosmetics.

The International Agency for Research on Cancer (on behalf of the World Health Organization) regards PFOA as being carcinogenic to humans and PFOS as possibly carcinogenic to humans.

Our guidelines

Australian drinking water supplies are assessed against national water quality standards. These Australian Drinking Water Guidelines are continuously reviewed by industry and health experts that scan the international literature and update them accordingly.

All city and town water supplies across Australia are subject to a wide range of physical and chemical water tests. The results are compared to Australian water guidelines.

Some tests relate to human health considerations, such as levels of lead or bacteria. Others relate to “aesthetic” considerations, such as the appearance or taste of water. Most water authorities across Australia make water quality information and compliance with Australian guidelines freely available.

What about Australian PFOS and PFOA standards?

These chemicals can enter our drinking water system from many potential sources, such as via their use in fire-fighting foams or pesticides.

According to the Australian Drinking Water Guidelines, PFOS should not exceed 0.07 micrograms per litre in drinking water. And PFOA should not exceed 0.56 micrograms per litre. One microgram is equivalent to one part per billion.

The concentration of these chemicals in water is incredibly small. And much of the advice on their concentration is provided in different units. Sometimes in micrograms or nannograms. The USEPA uses parts per trillion.

In parts per trillion (ppt) the Australian Guidelines for PFOS is 70 ppt and PFOA is 560 ppt. The USEPA’s new maximum contaminant levels (enforceable levels) are 4 ppt for both PFOS and also PFOA. Previous news reports have pointed out Australian guidelines for these chemicals in drinking water are up to 140 times higher than the USEPA permits.

Yikes! That seems like a lot

Today’s news report cites PFOS and PFOA water tests done at many different water supplies across Australia. Some water samples did not detect either chemicals. But most did, with the highest PFOS concentration 15.1–15.6 parts per trillion from Glenunga, South Australia. The highest PFOA concentration was reported from a small water supply in western Sydney, where it was detected at 5.17–9.66 parts per trillion.

Australia and the US are not alone. This is an enormous global problem.

One of the obvious challenges for the Australian water industry is that current water treatment processes may not be effective at removing PFOS or PFOA. The Australian Drinking Water Guidelines provide this advice:

Standard water treatment technologies including coagulation followed by physical separation, aeration, chemical oxidation, UV irradiation, and disinfection have little or no effect on PFOS or PFOA concentrations.

Filtering with activated carbon and reverse osmosis may remove many PFAS chemicals. But no treatment systems appear to be completely effective at their removal.

Removing these contaminants might be particularly difficult for small regional water supplies already struggling to maintain their water infrastructure. The NSW Auditor General criticised the planning for, and funding of, town water infrastructure in regional NSW back in 2020.

Where to from here?

The Australian water industry likely has little choice but to follow the US lead and address PFOS/PFAS contamination in drinking water. Along with lower thresholds, the US committed US$1 billion to water infrastructure to improve detection and water treatment. They will also now require:

Public water systems must monitor for these PFAS and have three years to complete initial monitoring (by 2027) […]

As today’s report notes, it is very difficult to find any recent data on PFOS and PFOA in Australian drinking water supplies. Australian regulators should also require ongoing and widespread monitoring of our major city and regional water supplies for these “forever chemicals”.

The bottom line for drinking tap water is to keep watching this space. Buying bottled water might not be effective (2021 US research detected PFAS in 39 out of 100 bottled waters). The USEPA suggests people can reduce PFAS exposure with measures including avoiding fish from contaminated waters and considering home filtration systems.

Correction: this article previously listed the maximum Australian Drinking Water Guidelines PFOA level as 0.056 micrograms per litre. The figure has been updated to show the correct level of 0.56 micrograms per litre.

Ian A. Wright, Associate Professor in Environmental Science, Western Sydney University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Hundreds of thousands of people worldwide are taking drugs like Ozempic to lose weight. But what do we actually know about them? This month, The Conversation’s experts explore their rise, impact and potential consequences.

Drugs like Ozempic are very effective at helping most people who take them lose weight. Semaglutide (sold as Wegovy and Ozempic) and tirzepatide (sold as Zepbound and Mounjaro) are the most well known in the class of drugs that mimic hormones to reduce feelings of hunger.

But does weight come back when you stop using it?

The short answer is yes. Stopping tirzepatide and semaglutide will result in weight regain in most people.

So are these medications simply another (expensive) form of yo-yo dieting? Let’s look at what the evidence shows so far.

It’s a long-term treatment, not a short course

If you have a bacterial infection, antibiotics will help your body fight off the germs causing your illness. You take the full course of medication, and the infection is gone.

For obesity, taking tirzepatide or semaglutide can help your body get rid of fat. However it doesn’t fix the reasons you gained weight in the first place because obesity is a chronic, complex condition. When you stop the medications, the weight returns.

Perhaps a more useful comparison is with high blood pressure, also known as hypertension. Treatment for hypertension is lifelong. It’s the same with obesity. Medications work, but only while you are taking them. (Though obesity is more complicated than hypertension, as many different factors both cause and perpetuate it.)

Therefore, several concurrent approaches are needed; taking medication can be an important part of effective management but on its own, it’s often insufficient. And in an unwanted knock-on effect, stopping medication can undermine other strategies to lose weight, like eating less.

Why do people stop?

Research trials show anywhere from 6% to 13.5% of participants stop taking these drugs, primarily because of side effects.

But these studies don’t account for those forced to stop because of cost or widespread supply issues. We don’t know how many people have needed to stop this medication over the past few years for these reasons.

Understanding what stopping does to the body is therefore important.

So what happens when you stop?

When you stop using tirzepatide or semaglutide, it takes several days (or even a couple of weeks) to move out of your system. As it does, a number of things happen:

• you start feeling hungry again, because both your brain and your gut no longer have the medication working to make you feel full

• blood sugars increase, because the medication is no longer acting on the pancreas to help control this. If you have diabetes as well as obesity you may need to take other medications to keep these in an acceptable range. Whether you have diabetes or not, you may need to eat foods with a low glycemic index to stabilise your blood sugars
• over the longer term, most people experience a return to their previous blood pressure and cholesterol levels, as the weight comes back
• weight regain will mostly be in the form of fat, because it will be gained faster than skeletal muscle.

While you were on the medication, you will have lost proportionally less skeletal muscle than fat, muscle loss is inevitable when you lose weight, no matter whether you use medications or not. The problem is, when you stop the medication, your body preferentially puts on fat.

Is stopping and starting the medications a problem?

People whose weight fluctuates with tirzepatide or semaglutide may experience some of the downsides of yo-yo dieting.

When you keep going on and off diets, it’s like a rollercoaster ride for your body. Each time you regain weight, your body has to deal with spikes in blood pressure, heart rate, and how your body handles sugars and fats. This can stress your heart and overall cardiovascular system, as it has to respond to greater fluctuations than usual.

Interestingly, the risk to the body from weight fluctuations is greater for people who are not obese. This should be a caution to those who are not obese but still using tirzepatide or semaglutide to try to lose unwanted weight.

How can you avoid gaining weight when you stop?

Fear of regaining weight when stopping these medications is valid, and needs to be addressed directly. As obesity has many causes and perpetuating factors, many evidence-based approaches are needed to reduce weight regain. This might include:

• getting quality sleep
• exercising in a way that builds and maintains muscle. While on the medication, you will likely have lost muscle as well as fat, although this is not inevitable, especially if you exercise regularly while taking it

• addressing emotional and cultural aspects of life that contribute to over-eating and/or eating unhealthy foods, and how you view your body. Stigma and shame around body shape and size is not cured by taking this medication. Even if you have a healthy relationship with food, we live in a culture that is fat-phobic and discriminates against people in larger bodies
• eating in a healthy way, hopefully continuing with habits that were formed while on the medication. Eating meals that have high nutrition and fibre, for example, and lower overall portion sizes.

Many people will stop taking tirzepatide or semaglutide at some point, given it is expensive and in short supply. When you do, it is important to understand what will happen and what you can do to help avoid the consequences. Regular reviews with your GP are also important.

Read the other articles in The Conversation’s Ozempic series here.

Natasha Yates, General Practitioner, PhD Candidate, Bond University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Can you imagine hearing yourself speak? A voice inside your head – perhaps reciting a shopping list or a phone number? What would life be like if you couldn’t?

Some people, including me, cannot have imagined visual experiences. We cannot close our eyes and conjure an experience of seeing a loved one’s face, or imagine our lounge room layout – to consider if a new piece of furniture might fit in it. This is called “aphantasia”, from a Greek phrase where the “a” means without, and “phantasia” refers to an image. Colloquially, people like myself are often referred to as having a “blind mind”.

While most attention has been given to the inability to have imagined visual sensations, aphantasics can lack other imagined experiences. We might be unable to experience imagined tastes or smells. Some people cannot imagine hearing themselves speak.

A recent study has advanced our understanding of people who cannot imagine hearing their own internal monologue. Importantly, the authors have identified some tasks that such people are more likely to find challenging.

What the study found

Researchers at the University of Copenhagen in Denmark and at the University of Wisconsin-Madison in the United States recruited 93 volunteers. They included 46 adults who reported low levels of inner speech and 47 who reported high levels.

Both groups were given challenging tasks: judging if the names of objects they had seen would rhyme and recalling words. The group without an inner monologue performed worse. But differences disappeared when everyone could say words aloud.

Importantly, people who reported less inner speech were not worse at all tasks. They could recall similar numbers of words when the words had a different appearance to one another. This negates any suggestion that aphants (people with aphantasia) simply weren’t trying or were less capable.

A welcome validation

The study provides some welcome evidence for the lived experiences of some aphants, who are still often told their experiences are not different, but rather that they cannot describe their imagined experiences. Some people feel anxiety when they realise other people can have imagined experiences that they cannot. These feelings may be deepened when others assert they are merely confused or inarticulate.

In my own aphantasia research I have often quizzed crowds of people on their capacity to have imagined experiences.

Questions about the capacity to have imagined visual or audio sensations tend to be excitedly endorsed by a vast majority, but questions about imagined experiences of taste or smell seem to cause more confusion. Some people are adamant they can do this, including a colleague who says he can imagine what combinations of ingredients will taste like when cooked together. But other responses suggest subtypes of aphantasia may prove to be more common than we realise.

The authors of the recent study suggest the inability to imagine hearing yourself speak should be referred to as “anendophasia”, meaning without inner speech. Other authors had suggested anauralia (meaning without auditory imagery). Still other researchers have referred to all types of imagined sensation as being different types of “imagery”.

Having consistent names is important. It can help scientists “talk” to one another to compare findings. If different authors use different names, important evidence can be missed.

We have more than 5 senses

Debate continues about how many senses humans have, but some scientists reasonably argue for a number greater than 20.

In addition to the five senses of sight, smell, taste, touch and hearing, lesser known senses include thermoception (our sense of heat) and proprioception (awareness of the positions of our body parts). Thanks to proprioception, most of us can close our eyes and touch the tip of our index finger to our nose. Thanks to our vestibular sense, we typically have a good idea of which way is up and can maintain balance.

It may be tempting to give a new name to each inability to have a given type of imagined sensation. But this could lead to confusion. Another approach would be to adapt phrases that are already widely used. People who are unable to have imagined sensations commonly refer to ourselves as “aphants”. This could be adapted with a prefix, such as “audio aphant”. Time will tell which approach is adopted by most researchers.

Why we should keep investigating

Regardless of the names we use, the study of multiple types of inability to have an imagined sensation is important. These investigations could reveal the essential processes in human brains that bring about a conscious experience of an imagined sensation.

In time, this will not only lead to a better understanding of the diversity of humans, but may help uncover how human brains can create any conscious sensation. This question – how and where our conscious feelings are generated – remains one of the great mysteries of science.

Derek Arnold, Professor, School of Psychology, The University of Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.