Health and exercise - weightlifting and bone density

Does weightlifting improve bone density?

Inti St Clair/Getty

Hunter Bennett, University of South Australia

You may have heard high-impact activity – exercise such as running, jumping, football and basketball – is good at building bone density and strength. But what about when you’re standing still, lifting weights at the gym?

The good news is weight training is great for bone health. But some exercises are more effective than others. Here’s what the science says.

What is bone density?

Bone density, also known as bone mineral density, is essentially a measure of how many minerals (such as calcium and phosphorus) are packed into your bones.

It gives you an indication of how solid your bones are, which is important because denser bones are generally less likely to break.

However, bone density is not quite the same as bone strength.

Bones also rely on a range of other compounds (such as collagen) to provide support and structure. So, even dense bones can become brittle if they are lacking these key structural components.

However, bone mineral density (measured with a bone scan) is still considered one of the best indicators of bone health because it is strongly linked to fracture risk.

While there is likely a genetic component to bone health, your daily choices can have a big impact.

What affects your bone health?

Research shows a few factors can influence how strong and dense your bones are:

Getting older: As we age, our bone mineral density tends to decrease. This decline is generally greater in women after menopause, but it occurs in everyone.

Nutrition: Eating calcium-rich foods – dairy in particular, but also many vegetables, nuts, legumes, eggs and meat – has been shown to have a small impact on bone density (although the extent to which this reduces fracture risk is unclear).

Exposure to sun: Sunlight helps your body make vitamin D, which helps you absorb calcium, and has been linked to better bone density.

Exercise: It is well established that people who do high-impact and high-load exercise (such as sprinting and weight training) tend to have denser and stronger bones than those who don’t.

Smoking: Older people who smoke tend to have lower bone density than those who don’t smoke.

Why does movement improve bone density?

In the same way that your muscles get stronger when you expose them to stress, your bones get stronger when they’re asked to handle more load. This is why exercise is so important for bone health – because it tells your bones to adapt and become stronger.

Many of us know that people at risk for bone loss – post-menopausal women and older adults – should be focused on exercising for bone health.

However, everyone can benefit from targeted exercise, and it’s arguably just as important to prevent declines in bone health.

In fact, whether you are male or female, the younger you start, the more likely you are to have denser bones into your older life. This is crucial for long-term bone health.

Do weights improve bone density?

Yes. One of the most effective exercises for bone health is lifting weights.

When you lift weights, your muscles pull on your bones, sending signals that encourage new bone formation. There is a large body of evidence showing weight training can improve bone density in adults, including in post-menopausal women.

But not all exercises are created equal. For example, some evidence suggests large compound exercises that place more load on the skeleton – such as squats and deadlifts – are particularly effective at increasing density in the spine and hips, two areas prone to fractures.

What type of weight training is best?

Lifting heavier weights is thought to produce better results than lifting lighter ones. This means doing sets of three to eight repetitions using heavy weights is likely to have a greater impact on your bones than doing many repetitions with lighter ones.

Similarly, it takes a long time for your bones to adapt and become denser – usually six months or more. This means for healthy bones, it’s better to integrate weight training into your weekly routine rather than do it in bursts for a few weeks at a time.

Exercises that use body weight, such as yoga and pilates, have many health benefits. However they are unlikely to have a significant impact on bone density, as they tend to put only light stress on your bones.

If you are new to weight training, you might need to start a bit lighter and get used to the movements before adding weight. And if you need help, finding an exercise professional in your local area might be a great first step.

Exercising for bone health is not complex. Just a couple of (heavy) weight training sessions per week can make a big difference.

If you’re concerned you have low bone density, speak to your doctor. They can assess whether you need to go for a scan.

Hunter Bennett, Lecturer in Exercise Science, University of South Australia

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

Environment - Climate Change - Extreme weather and declining tropical birdlife

70 years of data show extreme heat is already wiping out tropical bird populations

DeAgostini/Getty Images

James Watson, The University of Queensland; Maximilian Kotz, Barcelona Supercomputing Center-Centro Nacional de Supercomputación (BSC-CNS), and Tatsuya Amano, The University of Queensland

Human-driven climate change threatens many species, including birds. Most studies on this topic focus on long-term climate trends, such as gradual rises in average temperatures or shifts in rainfall patterns. But extreme weather events are becoming more common and intense, so they warrant further attention.

Our new research shows extreme heat is having a particularly severe effect on tropical birds. We found increased exposure to extreme heat has reduced bird populations in tropical regions by 25–38% since 1950.

This is not just a temporary dip – it’s a long-term, cumulative effect that continues to build as the planet warms.

Our research helps explain why bird numbers are falling even in wild places relatively untouched by humans, such as some very remote protected tropical forests. It underscores the urgent need to reduce greenhouse gas emissions, to conserve the remaining biodiversity.

Digging into huge global datasets

We analysed data from long-term monitoring of more than 3,000 bird populations worldwide between 1950 and 2020. This dataset captures more than 90,000 scientific observations.

Although there are some gaps, the dataset offers an unmatched view of how bird populations have changed over time. Some parts of the world such as western Europe and North America were better represented than others, but all continents were covered.

We matched this bird data with detailed daily weather records from a global climate database that stretches back to 1940. This allowed us to track how bird populations responded to specific changes in daily temperatures and rainfall, including extreme heat.

We also looked at average yearly temperatures, total annual rainfall, and episodes of unusually heavy rainfall.

Using another dataset that reflects human industrial activity over time, we accounted for human pressures such as land development and human population density.

By combining all these sources of data, we created computer models to evaluate how climate factors and human impacts influence bird population growth.

Our research confirmed the work of other climate scientists showing extreme heat events have increased dramatically over the past 70 years, especially near the equator.

Birds in tropical regions are now experiencing dangerously hot days about ten times more often than they did in the past.

Tropical birds have experienced a 10-fold increase in exposure to extreme heat over the past 60 years. Kotz, M. et al. (2025) Nature Ecology & Evolution

What we found: extreme heat is the biggest climate threat to birds

While changes in average temperature and rainfall do affect birds, we found the increasing number of dangerously hot days had the greatest effect – especially in tropical regions.

This is a major concern because tropical birds often have small home ranges and are highly specialised in terms of the habitats and climates they persist in. In many cases tropical birds exist within a small range of heat tolerance.

At temperatures beyond a bird’s limit of endurance, they go into hyperthermia, where their body temperature rises uncontrollably. In this state, birds may adopt a drooped-wing posture to expose more skin for heat loss, hold their beaks open and pant rapidly, spread their feathers, and become lethargic or disoriented. In severe cases, they lose coordination, fall from perches, or even collapse unconscious.

A black-collared barbet (Lybius torquatus) from Botswana. Sergey Dereliev

If they survive the experience, they can suffer long-term damage such as heat-induced organ failure and reduced reproductive capacity. Heat exposure reduces breeding success by lowering adult body condition and reducing time spent foraging – because the birds must rest or seek shade during the hottest hours.

It also causes heat stress in eggs and nestlings. In extreme events, nestlings may die from hyperthermia, or parents may abandon nests to save themselves.

Heat also increases a bird’s demand for water — not because they sweat (birds lack sweat glands) but because they lose water rapidly through evaporative cooling. This happens mainly via panting (respiratory evaporation) and, in some species, gular fluttering (rapid vibration of throat skin to increase airflow), as well as evaporation through the skin. As temperatures climb, these processes accelerate, causing significant dehydration unless birds can drink more frequently or access moister food.

Our study found that across tropical areas, the impact of climate change on birds is perhaps even greater now than the impact of direct human activities such as logging, mining or farming. This is not to say habitat destruction due to these activities is not a serious issue – it clearly is a major concern to tropical biodiversity. But our study highlights the challenges climate change is already bringing to birds in tropical regions.

Extreme heat is bad for birds in more than one way. James Watson, Maximilian Kotz and Tatsuya Amano with icons from Flaticon, design by Canva.

A clear warning

Our research highlights the importance of focusing not just on average climate trends, but also on extreme events. Heatwaves are no longer rare, isolated incidents – they are becoming a regular part of life in many parts of the world.

If climate change continues unchecked, tropical birds – and likely many other animals and plants – will face increasing threats to their survival. Change may be too fast and too extreme for many species to adapt.

And as tropical regions host a huge share of the world’s biodiversity, including nearly half of all bird species, the ripple effects could be far-reaching.

Conservation strategies must take this into account. Protecting habitats from human industrial development remains important, but it’s no longer enough on its own. Proactive action to help species adapt to climate change needs to be part of wildlife protection plans – especially in the tropics.

Ultimately if we are to preserve global biodiversity, slowing down and eventually reversing climate change is essential. That means cutting greenhouse gas emissions, investing in ways to draw down existing carbon dioxide levels, and supporting policies that reduce our impact on the planet. The fate of tropical birds – and countless other species – depends on it.

Tropical bird population declined by one-third since 1980 due to climate change, featuring the study’s lead author Maximilian Kotz (Potsdam Institute for Climate Impact Research)

James Watson, Professor in Conservation Science, School of the Environment, The University of Queensland; Maximilian Kotz, Marie Curie Postdoctoral Research Fellow, Barcelona Supercomputing Center-Centro Nacional de Supercomputación (BSC-CNS), and Tatsuya Amano, Associate Professor, School of the Environment, The University of Queensland

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

Climate change - city heatwaves increase when polluting aerosols are reduced

   aerosol cover in cities                    Shutterstock

In one of the more perverse impacts of environmental monitoring and pollution control, researchers have found that heatwaves increase as harmful aerosol pollution is reduced for the purpose of obtaining cleaner air. The warming has been found to be greater in populated locations where, commensurately, there tends to be more air pollution.

Aerosols cause lower temperatures as they reflect sunlight away from the planet either through altering the cloud composition or as a direct effect. Cleaning up the air and removing aerosols for better human health has resulted ironically in increasing heatwaves and generally warming the climate. Researchers have found that for most of last century, heatwave frequency was slowed despite rising greenhouse gas emissions. This changed from 2005 as declines in polluting aerosols became more apparent. A related issue is that aerosol pollution may have masked up to half the warming effect of greenhouse gas emissions up till now. The net impact has been that aerosol reduction has added heatwaves across the planet by approximately two days per decade.

The research Article can be accessed at this link: Anthropogenic aerosol changes disproportionately impact the evolution of global heatwave hazard and exposure

Climate Change and Australia's Great Barrier Reef

World’s biggest coral survey confirms sharp decline in Great Barrier Reef after heatwave

Daniela Ceccarelli, Australian Institute of Marine Science; David Wachenfeld, Australian Institute of Marine Science, and Mike Emslie, Australian Institute of Marine Science

Official analysis of 124 reefs on the Great Barrier Reef shows coral cover has dropped sharply after a record-breaking marine heatwave in 2024, prompting grave fears over the trajectory of the natural wonder.

Over the past few years, fast-growing corals had pushed the Great Barrier Reef’s coral cover to record highs. But those corals were known to be extremely vulnerable and one bad summer away from losing those gains.

Our new report by the Australian Institute of Marine Science (AIMS) shows these fears have been realised. The percentage of living hard coral covering the Great Barrier Reef’s surface dropped in each region we surveyed.

The recent extreme highs and lows in coral cover are a troubling phenomenon. It raises the prospect that the Great Barrier Reef may reach a point from which it cannot recover.

Another global marine heatwave

In healthy corals, tiny algae produce both the coral’s main food source and its vibrant colours. When the water gets too warm, the algae are expelled and the coral’s tissue becomes transparent – revealing the white limestone skeleton beneath. This is called coral bleaching.

Coral can recover if temperatures are reduced and the relationship with the algae is restored, but it’s a stressful and difficult process. And if recovery takes too long, the coral will die.

In June 2023, a marine heatwave bleached coral reefs from the Caribbean to the Indian and Pacific Oceans.

It reached Australia’s east coast in February 2024, causing extensive coral bleaching. Aerial surveys showed three quarters of 1,080 reefs assessed had some bleaching. On 40% of these reefs, more than half the corals were white.

In the aftermath, in-water surveys measured how much coral died in the northern, central and southern Great Barrier Reef. The worst damage lined up with the highest levels of heat stress.

Sharp declines in coral cover

AIMS has surveyed reefs of the Great Barrier Reef each year since 1986, in a project known as the Long-Term Monitoring Program. It is the most extensive record of coral status on any reef ecosystem in the world.

One component of the surveys involves towing an expert observer behind a boat around the full perimeter of each reef. The observer records the amount of live, bleached and dead coral. These observations are then averaged for each location, and for each of the three regions of the Great Barrier Reef.

After each monitoring season we report on the percentage of living hard coral covering the Great Barrier Reef’s surface. It’s a coarse but robust, reliable indicator of the state of the Great Barrier Reef.

Coral losses this year were not uniform across the Great Barrier Reef. On the northern Great Barrier Reef, from Cape York to Cooktown, average coral cover dropped by about a quarter between 2024 and 2025 (from 39.8% to 30%). The largest declines on individual reefs (up to 70% loss) occurred near Lizard Island.

Reefs with stable or increasing coral cover were mostly found in the central region, from Cooktown to Proserpine. However, there was still a region-wide decline of 14% (from 33.2% to 28.6%), and reefs near Cairns lost between 17-60% of their 2024 coral cover.

In the southern reef (Proserpine to Gladstone) coral cover declined by almost a third. In the summer of 2024, southern reefs experienced the highest levels of heat stress ever recorded, resulting in substantial coral loss (from 38.9% to 26.9%).

The declines in the north and south were the largest in a single year since monitoring began 39 years ago.

Despite these losses, the Great Barrier Reef still has more coral than many other reefs worldwide, and remains a major tourist attraction. It’s possible to find areas that still look good in an ecosystem this huge, but that doesn’t mean the large-scale average hasn’t dropped.

More frequent bleaching events

Mass coral bleaching is becoming more frequent as the world warms.

Before the 1990s, mass bleaching was extremely rare. That changed in 1998 with the first major event, followed by another in 2002.

Back-to-back bleaching events occurred for the first time in 2016 and 2017. Since then, bleaching has struck the Great Barrier Reef in 2020, 2022, 2024, and again this year. The impacts of this year’s bleaching event will be revealed following the next round of surveys.

The time between these events is shrinking, giving corals less time to recover. Cyclones and crown-of-thorns starfish are also continuing to cause widespread coral loss.

You’ll see in the following charts how the percentage of coral cover has changed over time. The vertical yellow lines show the mass coral bleaching events increasing in frequency.

Confronting questions

The coral reefs of the future are unlikely to look like those of the past. The loss of biodiversity seems inevitable.

But will the reefs of the future still sustain the half a billion people that depend on them for food and income? Will they continue to protect coastlines from increasing storm activity and rising sea levels? These are confronting questions.

Effective management and research into reef adaptation and recovery interventions may bridge the gap until meaningful climate action is achieved. But above all, the key to securing a future for coral reefs is reducing greenhouse gas emissions.

Daniela Ceccarelli, Reef Fish Ecologist, Australian Institute of Marine Science; David Wachenfeld, Research Program Director – Reef Ecology and Monitoring, Australian Institute of Marine Science, and Mike Emslie, Senior Research Scientist in Reef Ecology, Australian Institute of Marine Science

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

The next UN Climate Change Conference - COP30 in Brazil

 
The 30th Conference of the Parties (COP) for the United Nations Framework Convention on Climate Change will be hosted by Brazil from 10th to 21st November 2025 in Belem, the capital of the state of Para. The city is located close to the Amazon, a crucial location given the climate change impacts on that crucial ecosystem and life resource.  There has been disquiet in the UN about the venue for COP30 as Belem is regarded as economically poor with limited capacity for dealing with an international conference of the size and scale of the COPs. For example, additional transport routes have had to be constructed for COP30 straining resources in Belem and including road construction in the Amazon itself.

Brazil holds the presidency for COP30 and has called for a course-correction as efforts to address climate change and meet agreed commitments are falling well behind stating: "the world must exponentially scale and speed up efforts to meet the commitments we have made".

The second global stocktake will take place  at COP30 measuring countries progress towards meeting the goals of the Paris Agreement. The first stocktake occured at COP28 and the results were far from reassuring. 

Brazil has proposed an action agenda for COP30 comprising six themes with a total of 30 objectives. The six themes are:

1. Transitioning Energy, Industry and Transport
2. Stewarding Forests, Oceans and Biodiversity
3. Transforming Agriculture and Food Systems
4. Building Resiliance for Cities, Infrastructure and Water
5. Fostering Human and Social Development
6. Cross-cutting issues - Unleashing Enablers and Accelerators, including on Finance, Technology and Capacity Building 

The sheer number of objectives and the wide scale of the themes appear far too ambitious and complex to achieve meaningful results and complete international agreement. Tangible results and concrete international cooperation are now essential given the increasingly dire situation.

The COP30 website can be accessed: COP30 Website 

Environmental contamination on the Earth - PFAS chemicals and a new acid rain

                                                          Nature (c) 

Science journal Nature has published further evidence of the pervasive impact of PFAS chemicals in the environment with the detection of trifluoroacetic acid (TFA) across the world in lakes, rivers, bottled water, beer, cereal crops, animal livers, human blood, urine and so on. It's been found in leaves and needles from trees in Germany, Canadian Arctic ice cores and ground water in Denmark. The concentration levels of TFA are rising with concerning increases being five to ten-fold in plants in some countries as one consequence. The graph above from Nature illustrates the increase. 

TFA is being distributed around the world through rain and snow. Wherever it rains, TFA comes with the water. 

TFA is a defined as a 'forever chemical'  as natural processes cannot break the strong carbon-fluorine bonds, a charcteristics of many of the PFAS substances. What is not clear is the health and environment impact on living things on the planet from the long term exposure to this chemical. Other PFAS chemicals have already been found to be carcinogenic. Continuing surveillence is warranted. 

Climate change - the Earth is continuing to heat and has passed the 1.5°C target

Only 3 years left – new study warns the world is running out of time to avoid the worst impacts of climate change

Piers Forster, University of Leeds and Debbie Rosen, University of Leeds

Bad climate news is everywhere. Africa is being hit particularly hard by climate change and extreme weather, impacting lives and livelihoods.

We are living in a world that is warming at the fastest rate since records began. Yet, governments have been slow to act.

The annual global climate change conference of the parties (COP30) is just months away. All of the 197 countries that belong to the United Nations were supposed to have submitted updated national climate plans to the UN by February this year. These plans outline how each country will cut its greenhouse gas emissions in line with the legally binding international Paris Agreement. This agreement commits all signatories to limiting human-caused global warming to no more than 1.5°C above pre-industrial levels.

Governments must also bring their newly updated national climate action plans to COP30 and show how they plan to adapt to the impacts that climate change will bring.

But so far, only 25 countries, covering around 20% of global emissions, have submitted their plans, known as Nationally Determined Contributions. In Africa, they are Somalia, Zambia and Zimbabwe. This leaves 172 still to come.

The nationally determined contributions are very important in setting out countries’ short- to medium-term commitments on climate change. They also provide a direction of travel that can inform broader policy decisions and investments. Aligning climate plans with development goals could lift 175 million people out of poverty.

But arguably only one of the submitted plans – the UK’s – is compatible with the Paris Agreement.

We are climate scientists, and one of us (Piers Forster) leads the global science team that publishes the annual Indicators of Global Climate Change report. This report gives an overview of the state of the climate system. It is based on calculations of the net emissions of greenhouse gases globally, how these are concentrating in the atmosphere, how temperatures are rising on the ground, and how much of this warming has been caused by humans.

The report also looks at how extreme temperatures and rainfall are intensifying, how much the sea levels are rising, and how much carbon dioxide can still be emitted before the planet’s temperature exceeds 1.5°C more than it was in pre-industrial times. This is important because staying within 1.5°C is needed to avoid the worst impacts of climate change.

Our report shows that human-caused global warming reached 1.36°C in 2024. This boosted average global temperatures (a combination of human-induced warming and natural variability in the climate system) to 1.52°C. In other words, the world has already reached the level where it has warmed so much that it cannot avoid significant impacts from climate change. There is no doubt we are in dangerous waters.

Our dangerously hot planet

Although last year’s global temperatures were very high, they were also alarmingly unexceptional. The data speaks for itself. Continued record high levels of greenhouse gas emissions have led to rising atmospheric concentrations of carbon dioxide, methane and nitrous oxide.

The result is rising temperatures that are rapidly eating into the remaining carbon budget (the amount of greenhouse gases that can be emitted within an agreed time). This will be exhausted in less than three years at current levels of emissions.

We need to face this head on: the window to stay within 1.5°C is essentially shut. Even if we can bring temperatures back down in future, it will be a long and difficult road.

At the same time, climate extremes are intensifying, bringing long-term risks and costs to the global economy but also, importantly, people. The African continent is now facing its deadliest climate crisis in over a decade.

It would be impossible to imagine economies operating without fast access to trusted data. When share prices plummet or growth stalls, politicians and business leaders act decisively. None would tolerate outdated intelligence on sales or the stock market.

But when it comes to climate, the speed of climate change often outpaces the data available. This means fast decisions can’t be made. If we treated climate data as we do financial reports, panic would ensue after each dire update. But while governments routinely pivot when faced with an economic downturn, they have been far slower to respond to what key climate indicators – the Earth’s vital signs – are telling us.

What needs to happen next

As more countries develop their climate plans, it’s time for leaders across the globe to face the hard truths of climate science.

Governments need to have fast access to trusted climate data so that they can develop up-to-date national climate plans. The national climate plans need to take a global perspective too. This is really important for fairness and equity. For example, developed countries must acknowledge that they’ve emitted more greenhouse gases and take the lead in presenting ambitious mitigation efforts and in providing finance for other countries to decarbonise and adapt.

In Africa, the UN is hosting UNFCCC Climate Week in Addis Ababa in September. As well as making plans for COP30, there will be sessions on accessing climate finance and ensuring that the transition to zero human-caused carbon emissions by 2050 (net zero) is just and equitable. The summit also aims to support countries that are still working on their national climate plans.

If nationally determined contributions are implemented, the pace of climate change will slow down. This is vital not just for the countries – and economies – currently on the frontline against climate change, but for a functioning global society.

Just five of the G20 countries have submitted their 2035 plans: Canada, Brazil, Japan, the United States and the United Kingdom. But the G20 is responsible for around 80% of global emissions. This means that South Africa’s current G20 presidency can help to ensure that the world prioritises efforts to help developing countries finance their transition to a low-carbon economy.

Another worrying factor is that just 10 of the updated nationally determined contributions have reaffirmed or strengthened commitments to move away from fossil fuels. This means that national climate plans from the European Union, China and India will be key in testing their climate leadership and keeping the Paris Agreement’s 1.5°C temperature goals alive. Many other countries will be scrutinising what these countries commit to before they submit their own national climate plans.

The data in our report helps the world to understand not just what’s happened in recent years, but also what to expect further down the track.

Our hope is that these and other countries submit ambitious and credible plans well before COP30. If they do, this will finally close the gap between acknowledging the climate crisis and making decisive efforts to address it. Every tonne of greenhouse gas emissions matters.

Piers Forster, Professor of Physical Climate Change; Director of the Priestley International Centre for Climate, University of Leeds and Debbie Rosen, Research and Innovation Development Manager for the Priestley Centre for Climate Futures, University of Leeds

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

Sunscreens - Therapeutic Goods Administration Review of chemicals

How safe are the chemicals in sunscreen? A pharmacology expert explains

aquaArts studio/Getty

Ian Musgrave, University of Adelaide

Last week, the Therapeutic Goods Administration (TGA) released its safety review of seven active ingredients commonly used in sunscreens.

It found five were low-risk and appropriate for use in sunscreens at their current concentrations.

However, the TGA recommended tighter restrictions on two ingredients – homosalate and oxybenzone – to reduce how much can be used in a product. This is based on uncertainty about their potential effects on the endocrine system, which creates and releases hormones.

This news, together with recent reports some products may have inflated their claims of SPF coverage, might make Australians worried about whether their sunscreen products are working – and safe.

But it’s not time to abandon sunscreens. In Australia, all sunscreens must pass a strict approval process before going on the market. The TGA tests the safety and efficacy of all ingredients, and this recent review is part of the TGA’s continuing commitment to safety.

The greatest threat sunscreen poses to Australians’ health is not using it.

Australia has the highest incidence of melanoma and non-melanoma skin cancer worldwide, and approximately 95% of melanoma cases in Australia are linked to ultraviolet (UV) exposure.

Still, it’s understandable people want to know what’s in their products, and any changes that might affect them. So let’s take a closer look at the safety review and what it found.

What are the active ingredients in sunscreen?

There are two main types of sunscreen: physical and chemical. This is based on the different active ingredients they use.

An active ingredient is a chemical component in a product that has an effect on the body – basically, what makes the product “work”.

In sunscreens, this is the compound that absorbs UV rays from the Sun. The other ingredients – for example, those that give the sunscreen its smell or help the skin absorb it – are “inactive”.

Physical sunscreens typically use minerals, such as titanium dioxide and zinc oxide, that can absorb the Sun’s rays but also reflect some of them.

Chemical sunscreens use a variety of chemical ingredients to absorb or scatter UV light, both long wave (UVA) or short wave (UVB).

The seven active ingredients in this review are in chemical sunscreens.

Why did the TGA do the review?

Our current limits for the concentrations of these chemicals in sunscreen are generally consistent with other regulatory agencies, such as the European Union and the US Food and Drug Administration.

However, safety is an evolving subject. The TGA periodically reexamines the safety of all therapeutic goods.

Last year, the TGA revised its method of estimating sunscreen exposure to more closely model how skin is exposed to sunscreens over time.

This model considers how much sunscreen someone typically applies, how much skin they cover (whole body versus face and hands, or just face) and how it’s absorbed through the skin.

Given this new model – along with changes in the EU and US approaches to sunscreen regulation – the TGA selected seven common sunscreen ingredients to investigate in depth.

Determining what’s safe

When evaluating whether chemicals are safe for human use, testing will often consider studies in animals – especially when there is no or limited data on humans. These animal tests are done by the manufacturers, not the TGA.

To take into account any unforeseen sensitivity humans may have to these chemicals, a “margin of safety” is built in. This is typically a concentration 50–100 times lower than the dose at which no negative effect was seen in animals.

The sunscreen review used a margin of safety 100 times lower than this dose as the safety threshold.

For most of the seven investigated sunscreen chemicals, the TGA found the margin of safety was above 100.

This means they’re considered safe and low-risk for long-term use.

However, two ingredients, homosalate and oxybenzone, were found to be below 100. This was based on the highest estimated sunscreen exposure, applied to the body at the maximum permitted concentration: 15% for homosalate, 10% for oxybenzone.

At lower concentrations, other uses – such as just the hands and face – could be considered low-risk for both ingredients.

What are the health concerns?

Homosalate and oxybenzone have low acute oral toxicity – meaning you would need to swallow a lot of it to experience toxic effects, nearly half a kilogram of these chemicals – and don’t cause irritation to eyes or skin.

There is inconclusive evidence about oxybenzone potentially causing cancer in rats and mice – but only at concentrations to which humans will never be exposed via sunscreens.

The key issue is whether the two ingredients affect the endocrine system.

While effects have been seen at high concentrations in animal studies, it is not clear whether these translate to humans exposed to sunscreen levels.

No effect has been seen in clinical studies on fertility, hormones, weight gain and, in pregnant women, fetal development.

The TGA is being very cautious here, using a very wide margin of safety under worst-case scenarios.

What are the recommendations?

The TGA recommends the allowed concentration of homosalate and oxybenzone be reduced.

But exactly how much it will be lowered is complicated, depending on whether the product is intended for adults or children, specifically for face, or the whole body, and so on.

However, some sunscreens would need to be reformulated or warning labels placed on particular formulations. The exact changes will be decided after public consultation. Submissions close on August 12.

What about benzophenone?

There is also some evidence benzophenone – a chemical produced when sunscreen that contains octocrylene degrades – may cause cancer at high concentrations.

This is based on studies in which mice and rats were fed benzophenone well above the concentration in sunscreens.

Octocrylene degrades slowly over time to benzophenone. Heat makes it degrade faster, especially at temperatures above 40°C.

The TGA has recommended restricting benzophenone to 0.0383% in sunscreens to ensure it remains safe during the product’s shelf life.

The Cancer Council advises storing sunscreens below 30°C.

The bottom line

The proposed restrictions are very conservative, based on worst-case scenarios.

But even in worst-case scenarios, the margin of safety for these ingredients is still below the level at which any negative effect was seen in animals.

The threat of cancer from sun exposure is far more serious than any potential negative effect from sunscreens.

If you do wish to avoid these chemicals before new limits are imposed, several sunscreens are available that provide high levels of protection with little or no homosalate and oxybenzone. For more information, consult product labels.

Ian Musgrave, Senior Lecturer in Pharmacology, University of Adelaide

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

Climate Change - the Paris Agreement - Key Objectives

                                                                                                 Shutterstock

As the ongoing and often fractious debate over climate change and the environment swings to and fro, the Paris Agreement is usually cited emphasising the key target of limiting global temperature increases to no more than 1.5°C. This is an incorrect explanation as the phrasing in the agreement is more nuanced. The Paris Agreement, adopted in December 2015 at COP21 has three goals -

• to keep global temperature increase well below 2 degrees C with efforts to limit it to 1.5°C,
• to strengthen adaptation and resilience capacities
• to align financial flows with the other goals of the Agreement

The Paris Agreement is therefore aimed at preventing global temperatures increasing above 2 degrees C with a preference to limiting the increase to 1.5°C. The actual upper temperature increase to be avoided is 2°C not 1.5°C.

The Agreement requires all countries both developed and developing, to submit "Nationally Determined Contributions (NDCs)". The NDCs are defined by each country and and an explanation provided as to what actions the country intends to take to respond to climate change. The implementation of actions is to be accompanied by an enhanced transparency regime.

The overall purpose of the Paris Agreement is to give effect to the principles and role of the United Nations Framework Convention on Climate Change (UNFCC).

Climate Change and the Monsoon - impacts

Melting ice will strengthen the monsoon in northern Australia – but cause drier conditions north of the Equator

Sebnem Coskun/Anadolu via Getty Images

Corey J. A. Bradshaw, Flinders University; Cassandra Rowe, James Cook University, and Michael Bird, James Cook University

Almost two-thirds of the world’s population is affected by the monsoon – the annual arrival of intense rains in areas north and south of the Equator. These drenching rains tend to arrive during each hemisphere’s summer.

The East Asian monsoon north of the equator is the best known and best studied, because it affects the largest land area and the most people. But the southern Indo-Australian monsoon is vitally important to northern Australia, Indonesia and Papua New Guinea. To date, it has been studied much less.

To help fill this gap in knowledge, we analysed deep sediment from an unusual lagoon near Darwin in northern Australia. We looked at ancient pollen and chemical isotopes (different versions of the same chemical element) to look about 150,000 years back in time and glimpse changes to the monsoon. When types of pollen change, it tells us the monsoon has changed. Drier conditions favour the emergence of grasslands, while wetter climates favour forests.

Our new research suggests as the world gets hotter, the Indo-Australian monsoon will intensify and northern Australia will get wetter. This finding is consistent with research suggesting the East Asian monsoon could weaken, threatening agriculture and nature in heavily populated countries.

Location of Girraween Lagoon in monsoonal north Australia. Insert shows approximate dominant flows of the East Asian and Indo-Australian summer monsoons. Corey Bradshaw/Flinders University, CC BY-NC

The past held in a single lagoon

To examine how monsoons change over time, researchers drill sediment cores to track changes in pollen and chemical isotopes. For example, changes in hydrogen isotopes indicate changes in the intensity of the monsoon rain.

The problem is, these cores have to come from long-undisturbed lake sediments, because such places provide a continuous record of change.

To reconstruct past changes in monsoon patterns, undisturbed sediments have to be sampled carefully by extracting a thin “core” from the bottom sediments. Once researchers have this precious core, they can examine the changing proportions of pollen, chemical isotopes and other properties. The deeper you drill the core, the farther back in time you can look.

These exacting requirements are one reason the Indo-Australian monsoon is not as well understood as its northern cousin.

Fortunately, we have found one place which has kept a detailed environmental record over a long period: Girraween Lagoon on the outskirts of Darwin in the Northern Territory.

This lagoon was created after a sinkhole formed more than 200,000 years ago. It has contained permanent water ever since, and is slowly filling with sediment and pollen blown in from the surrounding landscape.

The 18-metre core from Girraween’s sediments gave us a 150,000-year record of environmental change in Australia’s northern savannahs.

It took hard work to extract the core from Girraween Lagoon.

Dipping into the past

If you walk around Girraween Lagoon today, you’ll see a tall and dense tree canopy with a thick grass understory in the wet season. But it hasn’t always been that way.

During the last ice age 20,000–30,000 years ago, the sea level was much lower and the polar ice caps much larger. As a result, the lagoon was more than 300 kilometres from the coast. At that time, the lagoon was surrounded by an open, grassy savannah with fewer, shorter trees.

A schematic showing the depth of the Girraween core and the associated time periods. Emma Rehn/Centre of Excellence for Australian Biodiversity and Heritage, CC BY-NC

About 115,000 years ago (and again 90,000 years ago), Australia was dotted with gigantic inland “megalakes”. At those times, the lagoon expanded into a large, shallow lake surrounded by lush monsoon forest, with almost no grass.

At times, tree cover changed radically. In fact, over one 3,000-year period, the percentage of tree pollen soared from 15% to 95%. That suggests a sweeping change from grassland to dense forest – meaning a switch from drier to wetter climate at a rate too fast to be explained by changes in Earth’s orbit.

Some of these changes are linked to the shifting distance between coastline and lagoon as well as predictable variation in how much solar energy reaches Earth.

A connection to the North Atlantic

Huge ice sheets covered large areas of the Northern Hemisphere during previous ice ages.

Remarkably, the evidence of their melting at the end of previous ice age was there in the sediment core from Girraween Lagoon.

When glacial ice melts rapidly, huge volumes of fresh water flood into the North Atlantic. These rapid pulses are known as Heinrich events. These pulses can shut down the warm Gulf Stream current up the east coast of North America. As a result, the Northern Hemisphere cools and the Southern Hemisphere warms.

Over the last 150,000 years, there have been 14 of these events. We could see evidence of them in the sediment cores. Every gush of fresh water in the Atlantic triggered higher rainfall over northern Australia because of the buildup of heat in the Southern Hemisphere as the Gulf Stream slowed.

What does this mean for the monsoon?

All this suggests the Indo-Australian monsoon will get more intense as the world gets hotter and more ice melts.

That would mean a wetter northern Australia. It could also bring more rainfall to other Australian regions, and neighbouring countries. At this stage, it’s too uncertain to predict what an intensifying monsoon would do to the southern parts of Australia.

We might already be seeing this shift. Weather records since the 1960s show northern Australia getting steadily wetter, and less rain in Australia’s southeast and southwest.

Trends in total annual rainfall in Australia from 1960 to 2020. Commonwealth of Australia Bureau of Meteorology, CC BY

What would this mean for people? Australia’s tropical north is not densely populated, which would reduce the human impact of an intensifying monsoon.

But while our research suggests the Indo-Australian monsoon strengthens during Heinrich events, earlier research has shown the East Asian and other Northern Hemisphere monsoons will weaken. Without reliable monsoonal rains, food and water supplies for billions of people could be at risk.

Corey J. A. Bradshaw, Matthew Flinders Professor of Global Ecology and Node Leader in the ARC Centre of Excellence for Indigenous and Environmental Histories and Futures, Flinders University; Cassandra Rowe, Senior Research Fellow, ARC Centre of Excellence for Indigenous and Environmental Histories and Futures, and College of Science and Engineering, James Cook University, and Michael Bird, JCU Distinguished Professor, ARC Centre of Excellence for Indigenous and Environmental Histories and Futures, James Cook University

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

Climate change - ice loss in Antarctica has serious implications

Antarctic summer sea ice is at record lows. Here’s how it will harm the planet – and us

An icebreaker approaches Denman Glacier in March, when there was 70% less Antarctic sea ice than usual. Pete Harmsen AAD

Edward Doddridge, University of Tasmania

On her first dedicated scientific voyage to Antarctica in March, the Australian icebreaker RSV Nuyina found the area sea-ice free. Scientists were able to reach places never sampled before.

Over the past four summers, Antarctic sea ice extent has hit new lows.

I’m part of a large group of scientists who set out to explore the consequences of summer sea ice loss after the record lows of 2022 and 2023. Together we rounded up the latest publications, then gathered new evidence using satellites, computer modelling, and robotic ocean sampling devices. Today we can finally reveal what we found.

It’s bad news on many levels, because Antarctic sea ice is vital for the world’s climate and ecosystems. But we need to get a grip on what’s happening – and use this concerning data to prompt faster action on climate change.

Sea ice around Antarctica waxes and wanes with the seasons, growing in the cold months and melting in warm ones. But this rhythmic cycle is changing.

What we did and what we found

Our team used a huge range of approaches to study the consequences of sea ice loss.

We used satellites to understand sea ice loss over summer, measuring everything from ice thickness and extent to the length of time each year when sea ice is absent.

Satellite data was also used to calculate how much of the Antarctic coast was exposed to open ocean waves. We were then able to quantify the relationship between sea ice loss and iceberg calving.

Data from free-drifting ocean robots was used to understand how sea ice loss affects the tiny plants that support the marine food web.

Every other kind of available data was then harnessed to explore the full impact of sea ice changes on ecosystems.

Voyage reports from international colleagues came in handy when studying how sea ice loss affected Antarctic resupply missions.

We also used computer models to simulate the impact of dramatic summer sea ice loss on the ocean.

In summary, our extensive research reveals four key consequences of summer sea ice loss in Antarctica.

1. Ocean warming is compounding

Bright white sea ice reflects about 90% of the incoming energy from sunlight, while the darker ocean absorbs about 90%. So if there’s less summer sea ice, the ocean absorbs much more heat.

This means the ocean surface warms more in an extreme low sea ice year, such as 2016 – when everything changed.

Until recently, the Southern Ocean would reset over winter. If there was a summer with low sea ice cover, the ocean would warm a bit. But over winter, the extra heat would shift into the atmosphere.

That’s not working anymore. We know this from measuring sea surface temperatures, but we have also confirmed this relationship using computer models.

What’s happening instead is when summer sea ice is very low, as in 2016, it triggers ocean warming that persists. It takes about three years for the system to fully recover. But recovery is becoming less and less likely, given warming is building from year to year.

Comparing an average sea ice summer (a) to an extreme low sea ice summer (b) in which there is less sea ice for wildlife and more sunlight is absorbed by the ocean. The ice shelf is more exposed to ocean waves, calving more icebergs. The ocean is also less productive and tourist vessels can make a closer approach. Doddridge, E., W., et al. (2025) PNAS Nexus., CC BY-NC-ND

2. More icebergs are forming

Sea ice protects Antarctica’s coast from ocean waves.

On average, about a third of the continent’s coastline is exposed over summer. But this is changing. In 2022 and 2023, more than half of the Antarctic coast was exposed.

Our research shows more icebergs break away from Antarctic ice sheets in years with less sea ice. During an average summer, about 100 icebergs break away. Summers with low sea ice produce about twice as many icebergs.

Antarctic ice sheets without sea ice are more exposed to waves. Pete Harmsen AAD

3. Wildlife squeezed off the ice

Many species of seals and penguins rely on sea ice, especially for breeding and moulting.

Entire colonies of emperor penguins experienced “catastrophic breeding failure” in 2022, when sea ice melted before chicks were ready to go to sea.

After giving birth, crabeater seals need large, stable sea ice platforms for 2–3 weeks until their pups are weaned. The ice provides shelter and protection from predators. Less summer sea-ice cover makes large platforms harder to find.

Many seal and penguin species also take refuge on the sea ice when moulting. These species must avoid the icy water while their new feathers or fur grows, or risk dying of hypothermia.

4. Logistical challenges at the end of the world

Low summer sea ice makes it harder for people working in Antarctica. Shrinking summer sea ice will narrow the time window during which Antarctic bases can be resupplied over the ice. These bases may soon need to be resupplied from different locations, or using more difficult methods such as small boats.

Supply ships typically unload their cargo directly onto the sea ice, but that may have to change. Jared McGhie, Australian Antarctic Division

No longer safe

Anarctic sea ice began to change rapidly in 2015 and 2016. Since then it has remained well below the long-term average.

The dataset we use relies on measurements from US Department of Defense satellites. Late last month, the department announced it would no longer provide this data to the scientific community. While this has since been delayed to July 31, significant uncertainty remains.

One of the biggest challenges in climate science is gathering and maintaining consistent long-term datasets. Without these, we don’t accurately know how much our climate is changing. Observing the entire Earth is hard enough when we all work together. It’s going to be almost impossible if we don’t share our data.

Antarctic sea ice extent anomalies (the difference between the long-term average and the measurement) for the entire satellite record since the late 1970s. Edward Doddridge, using data from the US NSIDC Sea Ice Index, version 3., CC BY

Recent low sea ice summers present a scientific challenge. The system is currently changing faster than our scientific community can study it.

But vanishing sea ice also presents a challenge to society. The only way to prevent even more drastic changes in the future is to rapidly transition away from fossil fuels and reach net zero emissions.

Edward Doddridge, Senior Research Associate in Physical Oceanography, University of Tasmania

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