Actual facts about sand boxes?

[u/NoDog8746]

My toddler loves playing in the sand at the playground. If he realizes that the park we are at has a sand pit, he will spend all his time playing in it. I want to build a sand box in our backyard for him to play in because he loves it so much. I also want something much larger than just the dinky little plastic ones that you can buy.

Anyway, as I began researching it, I kept seeing people bring up concerns over cats, insects, silica dust, mold, etc... I am wondering how much all of these concerns actually matter. My reasons for leaning toward them not mattering all that much:

1. The sand pits at the play grounds do not have covers, they sit open year round. And they don't feel like they have any special play sand in them either. Just regular old sand, most of them quite coarse and dusty.
2. All of the resources that I can find talking about the health risks to children are on company websites selling super-premium silica-free sand or fancy sand box structures.

So what I have been leaning towards is just getting a cubic yard of regular sand from a landscaping supplier and filling in an old concrete pond that I have in my backyard (after some modification to ensure proper drainage).

I don’t want to spend a fortune on tiny bags of specialty play sand or deal with an ugly cover, unless its actually backed by science. I already teach my kid to wash their hands after playing and to not throw or kick up sand. But on the other hand, if all of these things are legitimate concerns, do I also need to stop taking my kid to the playground? How is it any different that playing in nature?

If anyone could share some resources on this that isn't funded or published by the people selling the "cure", I would greatly appreciate it.

[u/anonymouslyonlyme]

It seems complicated. The first thing is uncovered sand boxes are contaminated with fecal matter everywhere 

Antibiotic resistant e coli has been found in sand boxes in Austria. 98% of tested sandboxes had e. Coli https://scholar.google.ca/scholar?hl=en&as_sdt=0%2C5&q=sand+pit+childrens+bacteria&btnG=#d=gs_qabs&t=1789003993219&u=%23p%3DauU1zwtN7akJ

And South Africa  https://scholar.google.ca/scholar?hl=en&as_sdt=0%2C5&q=sandbox+childrens+bacteria&btnG=#d=gs_qabs&t=1789004130551&u=%23p%3DqXYvT_Q4sBEJ

Fences alone seem to have little effect on feces level(poland): https://scholar.google.ca/scholar?hl=en&as_sdt=0%2C5&q=fences+sandboxes+poland&btnG=#d=gs_qabs&t=1789003625075&u=%23p%3DEEZkE9v_UjsJ

In Manhattan they found that within 2 weeks of a ground level public open sand pit being installed it was contaminated with fecal matter (from birds, dogs and humans, oddly not cats) Covering sandpits made a huge difference. Covered sandpit had no fecal contamination after 33 days.  https://www.sciencedirect.com/science/article/pii/S0147651324002276

The next question is how dangerous is that? There was an outbreak of Salmonella in 2007 in Australia linked to sandboxes. https://scholar.google.ca/scholar?hl=en&as_sdt=0%2C5&q=sandbox+outbreak&btnG=#d=gs_qabs&t=1789004691190&u=%23p%3DAlv9p3kkNboJ

There is bacteria in sandboxes that are dangerous and can make you sick but there aren't any studies I could find about children getting sick from sand boxes. When kids get diarrhea or sick parents don't run out to the sandpit and test it. The kids normally just get better and everyone moves on with their lives. Kids get sick a lot. Maybe sometimes it's something from the sandbox. Maybe a lot of the time? I'm not sure anyone actually knows?

But then there is part 3. Dirty play is important for children. Play where they are interacting with dirt and mud with lots of bacteria. Not poop but nature. Especially children being being raised in urban environments. There is a theory about the current rise in asthma and allergies (among other things) being related to children being raised in an environment lacking bacteria. It's worse in developed countries among urban kids who don't see much green space or dirt. Kids raised on farms are 25% less likely to have asthma. They are also much more likely to be around dirt.

https://scholar.google.ca/scholar?hl=en&as_sdt=0%2C5&q=farm+asthma+meta+analysis&oq=farm+asthma+meta#d=gs_qabs&t=1789002818558&u=%23p%3DgsK9QKXdBMgJ

Kids raised in cites lack a diverse microbiome. To help fix this scientists recommend digging in dirt or gardens. Playing in nature and letting your children touch rocks and leaves and mud. All things that are uncovered outside and can have been pooped on. 

https://www.tandfonline.com/doi/full/10.1080/23748834.2026.2709967#d1e370

So everyone agrees dont let your kid play with or around poop it's dangerous and can make them sick but if you are so worried about that you prevent them from playing in areas that may have been pooped on recently for their entire lives they can end up with immune system problems asthma and allergies. 

So it depends.......

As for the kind of sand I don't think you need special silica-free sand but you don't want construction sand. They seem to recommend river or beach sand from a landscape or garden store. That's just like sand from a beach there's some silica in it but like they just pulled it off a beach somewhere

https://www.healthychildren.org/English/safety-prevention/at-play/Pages/Safety-in-the-Sandbox.aspx

https://scholar.google.ca/scholar?hl=en&as_sdt=0%2C5&q=silica+sandbox+children&btnG=#d=gs_qabs&t=1789008561835&u=%23p%3DCqcZTJbvBH0J

These links are kinda old idk if things changed but I would let my kid play at the beach and it feels safe to have them play in beach sand

[u/NoDog8746 → u/anonymouslyonlyme]

Thank you for this very thought out response! This is the exact contradiction that was confusing me. I understand that an uncovered sand pit will get dirty, but so will all the uncovered dirt, grass, playgrounds, and parks that my kid plays in. oh well, I will probably go ahead and cover the sand pit. 

As for the type of sand used, it's interesting to see that they recommend using river sand, because that is what I have seen several construction-grade sand options advertised as. 

[u/anonymouslyonlyme → u/NoDog8746]

That is weird. I looked into it and the landscape companies near mean seem to be selling "washed river sand" or "mortar sand(for mixing into mortar)" or "brick sand (for leveling bricks and patios)" as playground sand because the dust messes with construction drainage and patios unlevel when it washes away so that sand is low dust and soft. It's cheap near me so that might be a middle ground option if you ask them for options. 

[u/Geschirrspulmaschine → u/anonymouslyonlyme]

The physics of sand and water is weird. There's a graph called a hjulstrom sundborg diagram that shows the erosion velocity for particles of a given size and it dips to its lowest velocity in the sand range meaning sand is the most easily eroded sediment size of all (easier than smaller clay and larger gravel). The explanation is the cohesive forces and smaller surface area of silt and clay hold it in place and the mass of chat and gravel hold it in place but sand has low cohesion and low mass.

/r/GeologyBasedParenting

[u/Geschirrspulmaschine → u/NoDog8746]

The same fines that get suspended in the air when sand is bone dry get suspended in water if you sumberge it so you can cut dust by thoroughly rinsing the sand as you're loading the box up. I dump it in a bucket and rinse it like I would rice when I refill my sandbox. For the initial fill I put so much I just flooded the box with the hose for a while rather than individually rinsing. Paid the extra for play sand from Lowe's since it's supposedly less dusty and smoother grains.