What's important here is not the "littering" as such but that people are being responsible.
I presume you want your son to be a responsible person in general so I'd focus on that and if he isn't too comfortable with what "responsible" means yet feel free to substitute "good or bad" as appropriate.
TL;DR - Work with your son to see how hard it is to put an empty bottle back into your pocket compared to taking it out. Explain to him that because of this it would slow the racers down a lot so instead they arrange before the race for someone to come round after them and pick everything up again, hence the rubbish still ends up in the bin.
What we want to do is communicate this to your son in a way that he will understand how throwing your waste on the ground (littering in his eyes) can be done responsibly and to do so I recommend explaining it as an answer to his question; split into two part:
- Why don’t they deal with their rubbish by keeping it in their pockets?
- Why is it ok for them to deal with their rubbish by throwing it away?
Here is how I would approach it:
Yes, you’re right, the cyclists are throwing their bottles and
chocolate wrappers on the ground but this is because putting it back
in their pocket when empty is a lot harder than taking it out. Let’s
give it a try and see how hard it is!
You can have him try this with a pair of jeans (or any trousers that have tight pockets) and his own bottle of water:
- Put the water in his pocket for him and ask him to take it out and take a drink, he should manage this easily.
- Then, place the water back in his pocket and ask him to do it again but this time he needs to put the water back in his pocket, he will likely struggle with this if his pockets are tight.
- If he still finds it easy, or you really want to drive the point home, put the water back and ask him to try with 1 hand; with tight pockets a 4 year old should find this near impossible!
- Finally, tell him you want him to do it on his bike whilst cycling down the street! Don’t make him do it of course, but hopefully he’ll make the connection himself as to just how hard that would be given how hard cycling is already!
Now that you have both agreed that it is really hard to put these items back in your pocket you can look at what they do instead and why it is ok:
Because the cyclists are focusing so hard on winning the race they
cannot stop and put the bottles back in their pockets, they need to do
something that will let them get rid of their bottles but keep them
cycling really, really fast.
So what they do is all the racers agree
to get a team of people to follow behind them, right at the back, and
it is their job to collect up all the bottles and papers that are
dropped. This way, even though the cyclists know throwing it on the
ground is not a responsible thing to do, they have people that we
don't see on the TV that go round afterwards and pick up all the
things they have dropped.
If you end up in a big, important race one day then you might end up
with one of these people there to help you as well. Until then though,
you'll need to keep your own rubbish so you can get rid of it
responsibly yourself, even if it means holding onto it during your race.
You might find that next time he is out on his bike he actually convinces one of his friends to be this person and I'd encourage this, it's part of learning through play and making sense of what he's learned.
If you see this though just make sure he knows that this rubbish has to be picked up so he has to pick someone he knows is responsible and will definitely pick it up. If he knowingly picks someone who will likely just leave it it's just as bad as him leaving it himself!
I'd take this approach because it combines multiple, well established methods of teaching and learning:
We have Positive Reinforcement - by praising and acknowledging the fact he knows littering in wrong and that he has managed to correctly identified people doing it (given his understanding at the time).
We have Learning Through Play - by turning the challenge of putting your water bottles back into your pocket which helps keep in engaged and make sense of what you are explaining to him.
And we have Parent and Child Sharing a Hobby Together - ok, you were doing this already by just watching the cycling together, but we can jump on the back of that (hopefully without sucking the fun out of it by making it educational!) to learn over something you are both passionate about which helps reinforce the 'lesson' and really make it stick.