cyccommute 

Not likely. Burning of waste isn’t a wide spread practice and even if it were, the products of incineration should be water and carbon dioxide if done properly. Microplastics is due to the break down on the plastics we put out in the world. UV light and oxygen work (i.e. weathering) to break the chemical bonds in plastics which causes the item to fall apart into smaller and smaller pieces. Eventually, given enough time, the pieces should break apart to the point where they are only carbon dioxide. The resistance of the microplastics to weathering are going to depend on the monomer used. Polyethylene terephthalate (PET) used in bottles is likely going to break down fastest because it has lots of reactive sites in the polymer. Polystyrene is equally as reactive. Polybutadiene used in rubber will break down slower but there is more of it used and more of it abraded by the road surface so there is much more of it around. Polyester will break down more slowly because it still has reactive sites but fewer and less energetic. Polypropylene is much less reactive than any of these having only carbon-carbon bonds which are difficult to break using just UV and oxygen.

PFAS or polyfluoroalkyl substances are called “forever chemicals” because they are almost noble…i.e. they don’t react with much of anything. That’s why we use them. You can destroy them by trying to burn them but they really don’t “burn”. They just decompose into really nasty stuff. Up to about 350°C (660°F), they are pretty much impervious to anything.

Micro plastics are defined as particle smaller than 5mm. That’s actually a rather large particle. Most of the microplastics found at high altitudes are the tiniest of particles…down to the micron (0.001mm) or submicron size…that can picked up by the wind and transported into the upper atmosphere. Some may even serve as nucleating sites for rain drops and/or snow flakes like dust particle do. The mass of these microplastics particles is in the range of nanograms. That’s 1 billionth of a gram. A single grocery bag could decompose to 6 billion microplastics particles. A single PET bottle could decompose to about 9 billion microplastics particles. You can start to see the problem. Even a little bit of plastic can result in a huge number of microplastics particles.

But those pale in comparison to what comes off tires. Tires put about 40 kg of rubber into the air per kilometer of road way per day. Per year, that 14.6 metric tons per km or 14.6 million grams or 1.4x10^16 nanogram sized particles per kilometer of road way. Given that there are 4.09 million miles of road in the US, that means there are 9.1x10^24 nanogram sized particles put into the air every year. That’s 98 million metric tons per year. Worldwide, we use 480 billion plastic bottles every year which, at 8 g per bottle, works out to 3.8 million metric tons per year and it takes quite a while for a bottle to break down to the nanogram sized particle. But that is worldwide. Worldwide rubber release is 980 million metric tons per year.

Consider how high that number would be if we still used bias ply tires on vehicles instead of radials. Bias ply tires heat up more than radials and wear faster by about 3 times. Those values above would be 3 times higher if bias tires were still the predominate tire.

Yea, it’s tires. People have proposed calling the current era the “Plastic Era”. Maybe we should call it the Rubber Era. But no PFAS was used or released by those tires.

cyccommute 

Mostly dumped. Very little solid waste is incinerated.

While disposal of the tire carcass is a problem, it’s not near the problem that airborne microplastics is. A tire (or bottle or food container or any other plastic item) in a landfill is protected against break down due to the methods we used to bury our trash. Our middens are designed to sequester the waste in a dry, anaerobic, sealed environment. Water, air, and light don’t really get into modern dumps. Without any of those (or even one of those), the plastic will lay there for centuries. If anything, we could go back and mine those trash heaps for valuable materials in the future. To paraphrase my geology teacher in college, “the difference between ore and dirt is how much stuff you can get out of the dirt”.

As for recycling of tires, that’s a tough nut to crack. We want tires that last up to miles and miles as well as years and years of friction so we don’t want them to be too delicate. If they fell apart easily…i.e. are easy to recycle…they wouldn’t last up to the conditions we expose them to. Plastics fall into a couple of categories…thermoplastic and thermoset plastics. Thermoplastics can be melted and reformed almost endlessly. Contaminates (food, drink, oils, etc.) get in the way but even those can be removed fairly easily…but not it’s not too economical to do so. But, over all, apply a little heat and you can make the same stuff or different stuff from the thermoplastic

Thermoset plastics are plastics that generally crosslink and form tough, durable items like tires. Unfortunately, those crosslinks make reforming the plastic into something else next to impossible. Heating them usually causes the crosslinks to become more dense and thus stronger. In a tire, heating the tire to reform it would also make it less “rubbery”. It’s fairly easy to make the rubber…technically an elastomer…become less elastic. In other words, it’s easy to make rubber into a hockey puck but the world doesn’t need a whole lot of hockey pucks. You can grind the tires up to make crumble for artificial turf but that seems to cause problems as per TLit’s original post. Most any other grinding of tires is going to have similar problems. But you can’t grind up the old tires to make new tires…at least not currently.

And that brings us back to mining landfills. Leave the material buried and work on ways of reusing it. Once it becomes something that someone can make money doing…i.e. capitalism…there will be a reason to mine those landfills.

Zara Sp00k

I guess the purpose of this thread is to create an argument, congrats, you have succeeded, but it's not like there isn't anything else to argue about.

In Florida there is a mountain of garbage they've given a name, Mount Trashmore, it is higher than as a 20 story building. Given how flat southern Florida, you can see it from 30 miles or more away. Some of the garbage mounds in Florida are so much higher than the surrounding that they have to put lights on them to warn pilots so they don't hit them. In south Florida, the highest points are all garbage dumps, only the foothills in the northern panhandle are higher.

I live in MN, just south of the Koch refinery (how fitting) they are two gynormous hills of garbage, it is fast becoming the highest point in the area.
Those big buckets of trash you put out every week, it all ends up somewhere.

cellery

Better put on a respirator and goggles and hermetically seal your laundry room every time you clean your dryer's lint trap then, because I have some vewy bad news for y'all about your dryer lint...

Zara Sp00k

I'm surprised California hasn't banned those fabric softener sheets that some people use in the dryer.
And what about all the spandex/lycra and cycling shoes that is thrown away? It's mostly made from fossil fuels.

Milton Keynes

Things could be worse. We could live in Beijing.

PeteHski

This is one of those things best put into the bigger picture. Where would tire dust rank in the overall list of air polluters and general health risks?

cyccommute 

Probably higher up than it used to be. Modern car technology (like 40 or 50 years ago “modern”) have significantly reduced the other pollutants. Catalytic converts have reduced the amount of unburned hydrocarbons and carbon monoxide. Fuel systems have been improved to keep unburned hydrocarbons from getting out of the vehicle. Even diesel engines are getting cleaner. Nothing has really been done to reduce tire dust.

Daniel4

Is anybody still wondering what forever chemicals are and how they end up in our bloodstream?

work4bike

Don't worry, because the flying car will be here by 2025