Ever since the footage from Blue Planet II hit our screens, there has been a growing awareness of the devastating impact of plastic on the marine environment. Anyone who has taken part in any of the Great British Beach Cleans organised by Marine Conservation Society volunteers will have already know much of the debris collected every year is plastic, from fish crates to drinks bottles, rope to the cotton bud sticks with cigarette butts thrown in for good measure. Whilst the MCS encourage volunteers to collect every item in a 100 metre stretch for their survey work, its certain that there are some plastic particles that are just too small to be picked up. These are the microplastics.
Microplastics are particles less than 5mm in size, ranging down to 5μm. That’s the Greek letter mu which represents micrometers, one million times smaller than a metre, a thousand times smaller than a millimetre. This size range is why these particles are called microplastics. Microplastics are not as easy to count. A collaboration between the University of Portsmouth and a charity called Just One Ocean is running a scheme to encourage people to survey their beaches for microplastics. There’s a carefully designed citizen science method to allow data from around the UK shores to be submitted and collated. We don’t fully understand the scale of the problem yet, but scientists from a number of disciplines are expressing concerns that it’s much larger than anyone suspected.
Microplastics have many sources. Large plastic pieces tumbling around in the marine environment will gradually break down into smaller and smaller pieces. Washing synthetic clothes in a washing machine releases microfibres into the waste water. If you run a tumble dryer you will know that you have to clear out the lint from it. That is just the larger fibres that get trapped. Smaller particles will enter the air blown out from the dryer. Microplastics have been found in the air, soil and water across the world. Since the 1960s, plastic particles were deliberately put into toothpastes and body care products as microbeads. They helped scrub the plaque off your teeth or acted as an abrasive layer to remove dead skin in facial scrubs. Those plastic beads were useful for about 2 minutes (because we all brush for the recommended time don’t we?) and when you rinsed and spat, those plastic beads were set free on the world. And the chances are they will exist long after you have gone.
We also find microplastics in food and bottled drinks. Filter feeding marine life picks up the particles from the environment. Mussels tested from 8 locations round the UK and samples bought from 8 UK supermarkets were all found to contain 70 microplastic particles per 100g of meat. Beer, honey and sea salt have also been shown to be good sources. Some studies have shown that over 80% of tap water samples contained microplastic and bottled water was even worse. One sample of bottled water had over 10,000 plastic particles in a litre. Science has a funny way of examining such issues, they’ve even looked at human faeces to gauge the levels that we are consuming. They found 20 microplastic particles for every 10g of stool sample.
So, what’s the big issue? Indestructible little bits of plastic that are so small you can’t see them with the naked eye? And they obviously pass through your intestine because they are too big to be absorbed. Why should anyone care? And to a certain extent we don’t fully know yet – and that may be the scariest aspect of this story.
When plastics are made, they aren’t a pure substance. Thousands of different chemical additives can be thrown into the recipe to manipulate the properties of the plastic. As large plastics breakdown, these additives are released. The other concern is that microplastics are very good at adsorbing (not absorbing) certain chemicals onto their surface. You might have heard of a few of these; PCBs, PAHs and DDT are on the detected list. We’re reasonably certain that probably 90% or more of the plastic microparticles that you’ve ingested have passed through your intestinal tract. But what scientists cannot quantify yet is whether they transferred damaging levels of toxins to you on the way. The data so far suggests possible disruption of your gut microbiome and inflammation. The consequences of long term repeated exposure to the toxic chemicals carried by the microplastics is still being assessed. It doesn’t bode well. We know from other species how devastating persistent organic pollutants can be.
There are estimated to have been 8.3 billion metric tonnes of plastic made since the 1960s, of which over 4.9 billion metric tonnes has been discarded into the environment. This is a problem that will not be easily solved and we are all at risk.
Before 1920, having tanned skin was associated with working outdoors and indicated that you carried out manual labour. The societal ideal was pale skin which showed that you were rich enough to stay indoors, although the pursuit of pale skin often involved powders containing lead and mercury, which weren’t exactly great choices from a health perspective. The Western Europe attitudes started to change in the 1920s when Coco Chanel started to popularise the idea of a tanned skin, and this trend accelerated through the explosion in cheap air travel from the 1960s, so that having a tan showed you could afford to take the time off work and lounge around catching some sun’s rays.
The concept of desirable skin colour varies around the world. Whites try to tan, whilst across Asia the sale of skin lightening creams and lotions is at an all time high. Your natural skin tone is determined by genetics and that is directly correlated to how much UV radiation you are exposed to. The higher the level of UV radiation, the darker the tone of indigenous skin. As some populations of humans moved to more northern latitudes there was a shift in genetics. With less UV radiation causing damage, there was a positive selection of individuals with lighter skin, who could synthesise more vitamin D. As societies changed from hunting to agriculture, there was a need to maximise the vitamin D synthesis to make up for the loss from the diet. About 40,000 years ago the mutations for pale skin emerged in both the East Asian and Western European populations.
The most important pigment in the skin is called Melanin. Specialised cells call Melanocytes make the pigment and pack it into the Keratinoctyes that make up a layer in the skin. Melanin is an important molecule as it controls the amount of UV radiation that can penetrate the skin. Some UV radiation is needed for vitamin D synthesis, but too much is harmful. UV light is divided into 3 different wavelengths of light, UV-A, UV-B and UV-C. UV-C and some UV-B are absorbed by the ozone layer in the atmosphere, which is a very good thing as without this absorption UV levels would be dangerously high (and quite possibly life on earth wouldn’t exist!). Some UV-B is absorbed by the epidermis (the upper layer of the skin but UV-A can penetrate further into the skin and interacts with the cells in the dermis. UV-B causes an increase in melanin production and UV-A causes the melanin molecules to change and become darker.
However, tanning is not the only consequence of UV exposure. Although no-one knew it during the 1960s, too much exposure to sunlight is the cause of 90% of all skin cancers, eye damage, immune system suppression and all the signs of ageing associated skin damage. As this message started to become understood, the tide has turned against tanning salons, and anyone out in the sun was urged to wear a hat, cover up exposed skin and slap on the sun cream….and then we hit another snag. In March 2018, Hawaii announced that it was bringing in laws to ban sun creams containing oxybenzone, which is the most widely used UV absorbing molecule in all sun creams in use today.
Once upon a time, Para-amino benzoic acid (PABA) was widely used in suncreams. Patented in the 1940s PABA was the first molecule to be used absorb UV-B in sun creams, but it fell out of favour as it stained clothes and caused allergic reactions. Then came Oxybenzone as the next generation molecule with the ability to absorb UV-A and UV-B. Oxybenzone isn’t just used in sun cream, but as a UV protection for a wide range of plastics too. Hawaii have recognised a study that showed that tiny amounts (microgrammes per litre) of oxybenzone cause coral larvae to stop moving around and prevented them from developing a hard skeleton. To understand the concept of just how toxic this is, that’s lethal levels at half a teaspoon in an Olympic sized swimming pool.
It’s time for a switch away from the UV absorbing molecules like PABA (still in use as the derivative padimate O) and oxybenzone. Perhaps we need to return to the mineral reflective suncreams with their chalky finish. Have a look at the label on your suncream. There are several alternatives hitting the market now, although for some of them the claims can be hard to verify. Perhaps the safest option for us and the environment would be to take the lesson from Victorian society and just cover up? Stop putting any plastic solutions into the sea including the lotions you slather on.
Michelle has been scuba diving for nearly 30 years. Drawing on her science background she tackles some bits of marine science. and sometimes has a sideways glance at the people and events that she encounters in the diving world.