Microplastics are defined as being plastic particles less than 5 mm in size and have permeated/infiltrated
nearly every part of the environment, including food, water, and air. Multiple recent
studies published in peer-reviewed journals such as Nature Medicine and Environmental
Science & Technology have shown mounting concern about their potential
impacts on human health as well as the survival of multiple species of wildlife on the planet.
The use of plastics remains almost out of control despite effects to reduce the use of soft plastic shopping bags and plastic drinking straws. As a result the contamination from microplastics has become both widespread and continuing.
Exposure pathway
Humans are exposed to microplastics primarily
through:
Ingestion: Found in seafood, bottled water, salt, and even vegetables.
Inhalation: Airborne microplastics from synthetic textiles and urban dust.
Dermal
contact: Though less studied, skin exposure may occur
via some types of cosmetics or contaminated water.
The biological effects of microplastic exposure
Once inside
the body, microplastics can interact with tissues and cells in several harmful
ways:
Inflammation and oxidative stress: Studies show that microplastics can trigger immune responses and
generate reactive oxygen species, leading to cellular damage.
Disruption of gut microbiota: Ingested microplastics may alter the composition of intestinal
flora, affecting digestion and immunity.
Translocation to organs: Nanoplastics (smaller than 1 µm) can cross biological barriers
and accumulate in organs such as the liver, kidneys, and brain.
Physical and chemical hazards of microplastics
Microplastics
are not inert and these substances carry:
Additives: Plasticizers, flame retardants, and stabilizers that may be
endocrine disruptors.
Adsorbed pollutants: Persistent organic pollutants (POPs) and heavy metals that bind
to plastic surfaces.
Physical abrasiveness: Their shape and size can cause mechanical irritation in tissues.
A 2025
review in Nature Medicine highlights several key findings:
Microplastics have been detected in human
blood, placenta, and lung tissue.
The toxicity depends on polymer type,
particle size, shape, and surface chemistry.
The presence of a biocorona, layer of proteins and biomolecules that forms around microplastics, can
influence how the body reacts to them.
Despite continuing research on microplastic infilration, there remains considerable knowledge gaps. Long term exposure and chronic impact studies, dose-reponse relationships including level of toxocity, and population-level epidemiogical data do not exist. In the interim, the only action that people can take is to reduce their reliance on plastic - whether this be in food storage items, utensils, bottles and when cooking (including microwave heating of plastic food trays).
Summer’s here and after a wet spring in many parts of Australia, mosquitoes are out in force. Insect repellent has become a routine requirement for time outdoors.
But how safe are they? And do we really need them?
The swelling and itchiness usually resolves in a few days. But scratching can result in secondary infection, especially for young children, if dirt and germs from underneath the fingernails get into the sore.
A mosquito bite can also cause disease. Not all diseases are life-threatening but they can be severely debilitating.
These diseases are a risk in most parts of Australia. Even cooler regions such as Victoria and Tasmania have mosquito-borne diseases which can be seriously debilitating.
Australian health authorities regularly review the recommendations for insect repellent use. But the range of formulations filling our supermarket shelves can change from summer to summer.
The Australian Pesticides and Veterinary Medicines Authority (APVMA) assesses insect repellents for their safety and effectiveness. Packaging should clearly display an APVMA registration number, along with directions for safe use and any required warnings, on their label.
Products sold as mosquito repellents in Australia must be registered with the Australian Pesticides and Veterinary Medicines Authority.Cameron Webb (NSW Health Pathology & University of Sydney), CC BY
What’s in popular mozzie repellents?
The most widely available active ingredients are diethyltoluamide (DEET), picaridin and oil of lemon eucalyptus (OLE).
Research and reviews from scientists and health authorities show mosquito repellents are a safe and effective way to prevent mosquito bites if used as recommended.
Scientists investigate each active ingredient to determine whether it’s safe. DEET has been the subject of many studies. Picaridin and oil of lemon eucalyptus haven’t been used for as long and haven’t been as thoroughly studied as DEET, but remain among those recommended by health authorities in Australia and overseas.
However, even if a product has been deemed safe, it is important to follow the directions for use on label. There will always be a risk if products are ingested in large quantities or intentionally misused.
What about babies and young children?
Most mosquito repellent formulations in Australia are registered for use on children over 12 months of age, although not all formulations list a specific age restriction.
International studies have shown that DEET and picaridin are safe for children. Recommended age limits for some mosquito repellents vary between countries and product type. In the United States, for example, there is no age limit for the use of DEET, while oil of eucalyptus is recommended only for children over three.
A 2024 study reviewing reports of adverse outcomes from mosquito repellent use concluded DEET was the preferred insect repellent for children, as it was the safest and offered long-lasting protection against biting mosquitoes when used as directed. The researchers noted other active ingredients may provide similar protections but more assessments were required to determine their safety.
Mosquito bites can be annoying but also lead to illness.A/Prof Cameron Webb (NSW Health Pathology & University of Sydney)
Tips for parents of babies and young children
Always be guided by the current recommendations of the APVMA and limit the use of DEET-based repellent from 12 months. Check the label before using mosquito repellent on children.
When you’re applying repellent, ideally apply it to your hands, then rub it on their skin. If you’re using a spray, apply it carefully and never directly onto a child’s face.
Unlike sunscreens, which have a SPF rating, there isn’t a single measure with which to compare the different formulations of mosquito repellents and their effectiveness.
“Heavy duty” or “tropical strength” formulations often contain the same active ingredients as those known as “kid friendly”, but in higher doses that last longer.
Lower concentrations still offer good mosquito bite protection, they just need to reapplied more often.
The secret to getting the best protection is to ensure mosquito repellents are applied correctly. Whether you use a cream, lotion, gel, roll-on, pump-spray or aerosol, make sure all exposed skin is covered. Reapply after swimming, sweaty exercise, or if it has rubbed off.
Cameron Webb, Clinical Associate Professor, School of Medical Science & Sydney Infectious Diseases Institute; Principal Hospital Scientist, University of Sydney
In various lifestyle magazines and health journals, the benefits of daily walking have often been cited with varying distances and number of steps mentioned. Good evidence and factual information is missing from many of the published articles leaving the reader wondering, how much should I do ? Research does exist and a summary of findings reveals there are some recommended step counts by age group -
Children and teens: 10,000 - 14,000 steps per day for growth and fitness (this would include playing sports so the number of steps would be easily achieved),
Adults under 60 years of age: 8,000 - 10,000 steps per day for optimal cardiovascular and metabolic health,
Adults over 60 years of age: 6,000 - 8,000 steps per day to reduce chronic disease and maintain mobility. The estimation of 3,000 steps per day to reduce the risk of Alzeheimers from the Harvard University study is also valid in this context.
Overall large scale studies have shown that 7,000 steps per day is an optimum level linked to significant reductions in mortality risk. This matches with epidemiologists' recommendations, highlighting a range of 6,000 - 8,000 steps as a method for reducing dementia risk with significant protection against memory and cognitive functional decline.
Around 56 million years ago, Earth suddenly got much hotter. Over about 5,000 years, the amount of carbon in the atmosphere drastically increased and global temperatures shot up by some 6°C.
As we show in new research published in Nature Communications, one consequence was that many of the world’s plants could no longer thrive. As a result, they soaked up less carbon from the atmosphere, which may have contributed to another interesting thing about this prehistoric planetary heatwave: it lasted more than 100,000 years.
Today Earth is warming around ten times faster than it did 56 million years ago, which may make it even harder for modern plants to adapt.
Rewinding 56 million years
Plants can help regulate the climate through a process known as carbon sequestration. This involves capturing carbon dioxide from the atmosphere via photosynthesis and storing it in their leaves, wood and roots.
However, abrupt global warming may temporarily impact this regulating function.
Investigating how Earth’s vegetation responded to the rapid global warming event around 56 million years ago – known formally as the Paleocene-Eocene Thermal Maximum (or PETM) – isn’t easy.
To do so, we developed a computer model simulating plant evolution, dispersal, and carbon cycling. We compared model outputs to fossil pollen and plant trait data from three sites to reconstruct vegetation changes such as height, leaf mass, and deciduousness across the warming event.
The three sites include: the Bighorn Basin in the United States, the North Sea and the Arctic Circle.
We focused our research on fossil pollen due to many unique properties.
First, pollen is produced in copious amounts. Second, it travels extensively via air and water currents. Third, it possesses a resilient structure that withstands decay, allowing for its excellent preservation in ancient geological formations.
A shift in vegetation
In the mid-latitude sites, including the Bighorn Basin – a deep and wide valley amidst the northern Rocky Mountains – evidence indicates vegetation had a reduced ability to regulate the climate.
Pollen data shows a shift to smaller plants such as palms and ferns. Leaf mass per area (a measure of leaf density and thickness) also increased as deciduous trees declined. Fossil soils indicate reduced soil organic carbon levels.
The data suggest smaller, drought-resistant plants including palms thrived in the landscape because they could keep pace with warming. They were, however, associated with a reduced capacity to store carbon in biomass and soils.
In contrast, the high-latitude Arctic site showed increased vegetation height and biomass following warming. The pollen data show replacement of conifer forests by broad-leaved swamp taxa and the persistence of some subtropical plants such as palms.
The model and data indicate high-latitude regions could adapt and even increase productivity (that is, capture and store carbon dioxide) under the warmer climate.
A glimpse into the future
The vegetation disruption during the PETM may have reduced terrestrial carbon sequestration for 70,000-100,000 years due to the reduced ability of vegetation and soils to capture and store carbon.
Our research suggests vegetation that is more able to regulate the climate took a long time to regrow, and this contributed to the length of the warming event.
Global warming of more than 4°C exceeded mid-latitude vegetation’s ability to adapt during the PETM. Human-made warming is occurring ten times faster, further limiting the time for adaptation.
What happened on Earth 56 million years ago highlights the need to understand biological systems’ capacity to keep pace with rapid climate changes and maintain efficient carbon sequestration.
How many daily steps does it take to reduce the risk of serious disease and promote good health ? Apparently for some age groups, its less than originally thought. The oft-quoted 10,000 daily steps has long been unmasked as being based on no evidence or science at all but rather a Japanese marketing campaign. Recent studies with actual research and using live subjects concluded around 9,000 steps per day was optimum for good health.
A study from Harvard University has since found that older people and particularly those at risk of developing Alzheimer's disease require only 3,000 steps per day. The study team led by Wai-Ying Yau analysed physical activity data from 296 cognitively healthy people aged between 50 and 90 years of age. Using a step-tracking device and brain imaging to obtain a baseline measurement of misfolded proteins (tau and beta-amyloid) that are suspected of causing Alzheimers, the subjects were measured every two to three years for a period of between 3 and 14 years. The researchers found that the levels of accumulation of misfolded tau was substantially slowed by taking between 3,000 and 5,000 steps per day. The exercise had no effect on beta-amyloid however this protein is less implicated in causing Alzheimers than tau. Between 5,000 and 7,500 steps per day was even more effective with a reduction in cognitive decline of 54 per cent compared to being inactive.
Why is this exercise so effective ? The hypothesis is that exercise reduces inflammation which is associated as a key factor in Alzheimers. Blood flow is also boosted to the brain and levels of protective hormones are increased.
It wasn’t a comfortable process for the tens of thousands of delegates trying to hash out progress on climate change on the edge of the Amazon in Belém, Brazil. I experienced the challenges of the United Nations COP30 climate talks firsthand.
Delegates were hot and sweaty. Tech and aircon didn’t always work. Both flood and fire disrupted negotiations over the fortnight of negotiations. It drove home how climate change feels. But despite the discomfort, some progress was made.
Brazilian President Luiz Inácio Lula da Silva dubbed it the “COP of Truth”. Delegates did not shy away from the urgency of the moment as climate change intensifies and emissions continue to climb.
Progress was made on funding climate finance and adaptation to the changes already emerging. But efforts on ending reliance on fossil fuels faltered in the face of strong resistance by fossil fuel powers. Much progress in Belém happened outside the main talks.
So what did COP30 deliver?
At one stage it looked like COP30 might crack the hardest nut in climate policy – reaching agreement on phasing out fossil fuels. Nations agreed two years ago that it was necessary to move away from fossil fuels. But no plan had yet been devised to get there.
Brazil had a plan: build support for a roadmap to phase out fossil fuels, championed by President Lula and pushed strongly by Environment Minister Marina Silva. It drew support from more than 80 countries, including major fossil fuel exporters such as Norway and Australia. Anticipating pushback, Brazil worked to boost support outside the main talks before bringing the plan in.
It didn’t work. By the end of COP30, all mention of a fossil fuel roadmap had been scrubbed from the text of the final outcomes, following fierce pushback from countries such as Russia, Saudi Arabia and India and many emerging economies.
Instead, countries agreed to launch “the Global Implementation Accelerator […] to keep 1.5°C within reach” and “taking into account” previous COP decisions. This initiative will be shepherded by the Brazilian COP30 Presidency and the leaders of next year’s COP31 talks, Turkey and Australia.
President Lula vowed to continue advocating for a fossil fuel roadmap at the G20. Colombia and the Netherlands will hold a conference on fossil fuel phaseout in April 2026. The COP30 decision text also makes reference to a “high-level event in 2026” which could take place in the Pacific. Without blockers of consensus at these meetings, a coalition of willing countries could make real progress in setting timelines and exchanging policy ideas for fossil fuel phase-out.
Brazil’s Environment Minister Marina Silva emerged as a quiet force working to build support for the first roadmap to phase out fossil fuel extraction and use.Aline Massuca/COP30, CC BY-NC-ND
The decision to develop a just transition mechanism was welcomed as a win for workers and communities. The new mechanism’s purpose will be to increase international cooperation, technical assistance, capacity-building and knowledge-sharing as countries shift towards a low carbon global economy.
Efforts to boost financing for climate adaptation bogged down, reflecting the trade-offs over fossil fuels.
These funds are meant to help nations most exposed to severe climate damage, usually poorer and with low emissions. These nations led the charge for a tripling of climate finance by 2030 from the US$40 billion (A$62 billion) agreed at COP26 four years ago. But the agreed text merely “calls for efforts to at least triple adaptation finance by 2035”, which pushes out the timeframe and has no funding baseline.
Funding for tropical forests
One of Brazil’s own initiatives, the Tropical Forest Facility, achieved greater success, securing US$9.5 billion (A$14.7 billion) in funding pledges – a COP record.
The trust fund for rainforests is designed to provide resources to arrest global deforestation and protect Indigenous lands, including in the Amazon’s vital carbon sink.
The success of these deforestation initiatives points to the effectiveness of the COP’s Action Agenda, aimed at spurring on climate action outside formal negotiations and including commitments from business, investors and civil society. As formal negotiations bog down, these bypasses may end up replacing negotiations in driving progress.
American absence
Ahead of COP30, analysts feared the ongoing attacks on climate action by the Trump administration would undermine the international negotiations.
But by summit’s end, the disappearance of the world’s biggest historical emitter and largest economy from negotiations had taken its toll.
Developing countries from the African group of negotiators argued better metrics and plans would be meaningless without funding to implement them. Traditionally, the US has been a major funder. No longer.
The US decision to turn its back on climate action created a subdued atmosphere. New finance pledges were broadly underwhelming, likely due to the dampening effect of the US retreat.
China’s negotiators focused most of their energy in pushing back on European trade measures targeting high-emissions products.Antonio Scorza/COP30, CC BY-NC-ND
Early on, many hoped renewables and clean tech giant China might fill the leadership void. China’s clean tech exports last year were enough to cut overseas emissions by 1%. The huge industrial power produces almost 32% of the world’s carbon emissions. These emissions have plateaued, in turn suggesting global emissions may now have peaked.
But China showed reluctance to take up the mantle, preferring to remain focused on its own domestic energy transition. Chinese negotiators spent most of their energy pushing back against new European trade measures targeting emissions-intensive production.
It was left to some of the smallest nations, Indigenous peoples and civil society to lead calls for sticking to the science, ramping up urgency and accelerating the rollout of solutions. An estimated 70,000 people marched in the streets of Belém, staging a mock funeral for fossil fuels. It was an important affirmation of widespread public support for climate action.
What legacy?
As the UN’s climate Executive Secretary Simon Stiell said midway through COP30, nations had to “give a little to get a lot”.
Many countries will be reflecting they gave a lot but got very little. The biggest winners were, yet again, the world’s petrostates who successfully frustrated attempts to address fossil fuels.
Questions will inevitably be asked over whether these consensus-based talks are fit for purpose, given they can be gamed by blockers.
For many, COP30 will be regarded as a failure on fossil fuels and addressing major gaps between national pledges to cut emissions and what’s needed to hold warming to 1.5°C.
This is true. But another view would be that these talks made real progress on important areas despite considerable challenges.
Negotiators from 194 countries showed up and continued to talk and work together to tackle the worsening crisis. Nearly half of those countries have shown they’re ready to begin weaning themselves off fossil fuels through their support for the phase-out roadmap. They don’t have to wait for a UN consensus to act. Fossil fuel exporters only have power while other nations buy and rely on their products.
The world’s climate talks are now clearly moving away from arcane negotiations to the pressing real-world challenges of doing the work. In a rapidly warming world, all issues are becoming climate issues.
