Sentinel Owl - Public Affairs Insight: environment, science, foreign affairs, economics & the arts
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| Microplastics on the shore GPT-5 AI generated |
Humans are exposed to microplastics primarily
through:
Once inside
the body, microplastics can interact with tissues and cells in several harmful
ways:
A 2025
review in Nature Medicine highlights several key findings:
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?
A bite from a mosquito can be itchy and irritating. Even a mild reaction can have us scratching, especially if you’re one of the people who are irresistible to mosquitoes.
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.
There are no specific cures for our local mosquito-borne diseases. While there is a vaccine available for Japanese encephalitis, preventing bites in the first place is the best way to prevent illnesses caused by Ross River, Murray Valley encephalitis and a range of other pathogens spread by mosquito bites.
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.
The most widely available active ingredients are diethyltoluamide (DEET), picaridin and oil of lemon eucalyptus (OLE).
Plant-derived products, including eucalyptus and tea tree oil, are also popular alternatives. These strongly smelling products are registered by the APVMA and provide some protection but need to be reapplied more frequently than other repellents.
Insect repellents are often thought to be unpleasant to use, or even a health risk themselves, but the inconvenience of using a repellent is easily outweighed by the benefit of reducing mosquito bites.
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.
Natural repellents, especially unregistered and DIY formulations, may may cause skin reactions or come with other risks, so stick with products that have been registered after being tested for safety or effectiveness.
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.
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.
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.
Don’t allow children to apply their own repellent, as it may lead to accidental ingestion or over-exposure.
When babies and toddlers are outdoors, consider using an insect net for strollers, prams or playpens.
While wrist bands, patches and stickers are marketed as mosquito repellents for children, there is little evidence they are effective. Smouldering devices, such as coils and sticks, aren’t a good idea when there is a chance of breathing in the smoke.
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
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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.
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.
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.
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.
Vera Korasidis, Lecturer in Environmental Geoscience, The University of Melbourne and Julian Rogger, Senior Research Associate, School of Geographical Sciences, University of Bristol
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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| GPT-5 AI generated |
