Mark Patrick Taylor, Macquarie University and Scott P. Wilson, Macquarie University

A recent study published in the prestigious New England Journal of Medicine has linked microplastics with risk to human health.

The study involved patients in Italy who had a condition called carotid artery plaque, where plaque builds up in arteries, potentially blocking blood flow. The researchers analysed plaque specimens from these patients.

They found those with carotid artery plaque who had microplastics and nanoplastics in their plaque had a higher risk of heart attack, stroke, or death (compared with carotid artery plaque patients who didn’t have any micro- or nanoplastics detected in their plaque specimens).

Importantly, the researchers didn’t find the micro- and nanoplastics caused the higher risk, only that it was correlated with it.

So, what are we to make of the new findings? And how does it fit with the broader evidence about microplastics in our environment and our bodies?

What are microplastics?

Microplastics are plastic particles less than five millimetres across. Nanoplastics are less than one micron in size (1,000 microns is equal to one millimetre). The precise size classifications are still a matter of debate.

Microplastics and nanoplastics are created when everyday products – including clothes, food and beverage packaging, home furnishings, plastic bags, toys and toiletries – degrade. Many personal care products contain microsplastics in the form of microbeads.

Plastic is also used widely in agriculture, and can degrade over time into microplastics and nanoplastics.

These particles are made up of common polymers such as polyethylene, polypropylene, polystyrene and polyvinyl chloride. The constituent chemical of polyvinyl chloride, vinyl chloride, is considered carcinogenic by the US Environmental Protection Agency.

Of course, the actual risk of harm depends on your level of exposure. As toxicologists are fond of saying, it’s the dose that makes the poison, so we need to be careful to not over-interpret emerging research.

A closer look at the study

This new study in the New England Journal of Medicine was a small cohort, initially comprising 304 patients. But only 257 completed the follow-up part of the study 34 months later.

The study had a number of limitations. The first is the findings related only to asymptomatic patients undergoing carotid endarterectomy (a procedure to remove carotid artery plaque). This means the findings might not be applicable to the wider population.

The authors also point out that while exposure to microplastics and nanoplastics has been likely increasing in recent decades, heart disease rates have been falling.

That said, the fact so many people in the study had detectable levels of microplastics in their body is notable. The researchers found detectable levels of polyethylene and polyvinyl chloride (two types of plastic) in excised carotid plaque from 58% and 12% of patients, respectively.

These patients were more likely to be younger men with diabetes or heart disease and a history of smoking. There was no substantive difference in where the patients lived.

Inflammation markers in plaque samples were more elevated in patients with detectable levels of microplastics and nanoplastics versus those without.

And, then there’s the headline finding: patients with microplastics and nanoplastics in their plaque had a higher risk of having what doctors call “a primary end point event” (non-fatal heart attack, non-fatal stroke, or death from any cause) than those who did not present with microplastics and nanoplastics in their plaque.

The authors of the study note their results “do not prove causality”.

However, it would be remiss not to be cautious. The history of environmental health is replete with examples of what were initially considered suspect chemicals that avoided proper regulation because of what the US National Research Council refers to as the “untested-chemical assumption”. This assumption arises where there is an absence of research demonstrating adverse effects, which obviates the requirement for regulatory action.

In general, more research is required to find out whether or not microplastics cause harm to human health. Until this evidence exists, we should adopt the precautionary principle; absence of evidence should not be taken as evidence of absence.

Global and local action

Exposure to microplastics in our home, work and outdoor environments is inevitable. Governments across the globe have started to acknowledge we must intervene.

The Global Plastics Treaty will be enacted by 175 nations from 2025. The treaty is designed, among other things, to limit microplastic exposure globally. Burdens are greatest especially in children and especially those in low-middle income nations.

In Australia, legislation ending single use plastics will help. So too will the increased rollout of container deposit schemes that include plastic bottles.

Microplastics pollution is an area that requires a collaborative approach between researchers, civil societies, industry and government. We believe the formation of a “microplastics national council” would help formulate and co-ordinate strategies to tackle this issue.

Little things matter. Small actions by individuals can also translate to significant overall environmental and human health benefits.

Choosing natural materials, fabrics, and utensils not made of plastic and disposing of waste thoughtfully and appropriately – including recycling wherever possible – is helpful.

Mark Patrick Taylor, Chief Environmental Scientist, EPA Victoria; Honorary Professor, School of Natural Sciences, Macquarie University and Scott P. Wilson, Research Director, Australian Microplastic Assessment Project (AUSMAP); Honorary Senior Research Fellow, School of Natural Sciences, Macquarie University

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

Throughout recorded history, our hair and nails played an important role in signifying who we are and our social status. You could say, they separate the caveman from businessman.

It was no surprise then that many of us found a new level of appreciation for our hairdressers and nail artists during the COVID lockdowns. Even Taylor Swift reported she cut her own hair during lockdown.

So, what would happen if all this hair and nail grooming got too much for us and we decided to give it all up. Would our hair and nails just keep on growing?

The answer is yes. The hair on our head grows, on average, 1 centimeter per month, while our fingernails grow an average of just over 3 millimetres.

When left unchecked, our hair and nails can grow to impressive lengths. Aliia Nasyrova, known as the Ukrainian Rapunzel, holds the world record for the longest locks on a living woman, which measure an impressive 257.33 cm.

When it comes to record-breaking fingernails, Diana Armstrong from the United States holds that record at 1,306.58 cm.

Most of us, however, get regular haircuts and trim our nails – some with greater frequency than others. So why do some people’s hair and nails grow more quickly?

Remind me, what are they made out of?

Hair and nails are made mostly from keratin. Both grow from matrix cells below the skin and grow through different patterns of cell division.

Nails grow steadily from the matrix cells, which sit under the skin at the base of the nail. These cells divide, pushing the older cells forward. As they grow, the new cells slide along the nail bed – the flat area under the fingernail which looks pink because of its rich blood supply.

A hair also starts growing from the matrix cells, eventually forming the visible part of the hair – the shaft. The hair shaft grows from a root that sits under the skin and is wrapped in a sac known as the hair follicle.

This sac has a nerve supply (which is why it hurts to pull out a hair), oil-producing glands that lubricate the hair and a tiny muscle that makes your hair stand up when it’s cold.

At the follicle’s base is the hair bulb, which contains the all-important hair papilla that supplies blood to the follicle.

Matrix cells near the papilla divide to produce new hair cells, which then harden and form the hair shaft. As the new hair cells are made, the hair is pushed up above the skin and the hair grows.

But the papilla also plays an integral part in regulating hair growth cycles, as it sends signals to the stem cells to move to the base of the follicle and form a hair matrix. Matrix cells then get signals to divide and start a new growth phase.

Unlike nails, our hair grows in cycles

Scientists have identified four phases of hair growth, the:

1. anagen or growth phase, which lasts between two and eight years
2. catagen or transition phase, when growth slows down, lasting around two weeks
3. telogen or resting phase, when there is no growth at all. This usually lasts two to three months
4. exogen or shedding phase, when the hair falls out and is replaced by the new hair growing from the same follicle. This starts the process all over again.

Each follicle goes through this cycle 10–30 times in its lifespan.

If all of our hair follicles grew at the same rate and entered the same phases simultaneously, there would be times when we would all be bald. That doesn’t usually happen: at any given time, only one in ten hairs is in the resting phase.

While we lose about 100–150 hairs daily, the average person has 100,000 hairs on their head, so we barely notice this natural shedding.

So what affects the speed of growth?

Genetics is the most significant factor. While hair growth rates vary between individuals, they tend to be consistent among family members.

Nails are also influenced by genetics, as siblings, especially identical twins, tend to have similar nail growth rates.

But there are also other influences.

Age makes a difference to hair and nail growth, even in healthy people. Younger people generally have faster growth rates because of the slowing metabolism and cell division that comes with ageing.

Hormonal changes can have an impact. Pregnancy often accelerates hair and nail growth rates, while menopause and high levels of the stress hormone cortisol can slow growth rates.

Nutrition also changes hair and nail strength and growth rate. While hair and nails are made mostly of keratin, they also contain water, fats and various minerals. As hair and nails keep growing, these minerals need to be replaced.

That’s why a balanced diet that includes sufficient nutrients to support your hair and nails is essential for maintaining their health.

Nutrient deficiencies may contribute to hair loss and nail breakage by disrupting their growth cycle or weakening their structure. Iron and zinc deficiencies, for example, have both been linked to hair loss and brittle nails.

This may explain why thick hair and strong, well-groomed nails have long been associated with perception of good health and high status.

However, not all perceptions are true.

No, hair and nails don’t grow after death

A persistent myth that may relate to the legends of vampires is that hair and nails continue to grow after we die.

In reality, they only appear to do so. As the body dehydrates after death, the skin shrinks, making hair and nails seem longer.

Morticians are well aware of this phenomenon and some inject tissue filler into the deceased’s fingertips to minimise this effect.

So, it seems that living or dead, there is no escape from the never-ending task of caring for our hair and nails.

Michelle Moscova, Adjunct Associate Professor, Anatomy, UNSW Sydney

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