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I'm seeing various articles on the web claiming that silica sand may be harmful to humans / cats, especially when inhaling the dust it creates.

Quartz silica (sand), the other ingredient in most clumping litters, is a known carcinogen for both humans and household pets when inhaled.

Source: https://www.care2.com/greenliving/the-dangers-of-clumping-cat-litter.html

This question was posted in 2010, so 9 years old already, maybe there's more literature on the subject by now?

I sometimes worry about breathing in the dust from cat litter. Have there been any studies or are there any health concerns on the danger of breathing in litter dust, either for me or my cats?

– April 15, 2010

https://www.drweil.com/health-wellness/balanced-living/pets-pet-care/is-kitty-litter-dangerous/

This one says research has shown without pointing to the actual research:

Sadly, silica litter puts our feline counterparts at risk whenever nature calls. Silica dust can be kicked up and inhaled by both cats and humans. what’s worse, silica crystals often stick to cats’ paws, and the dust frequently settles on their fur, leading to ingestion whenever a cat grooms itself. And while many clay litter users still aren’t fully aware of the dangers associated with crystalline silica, the research is decidedly more certain.

https://www.swheatscoop.com/the-dirt-on-dust-the-dangers-of-crystalline-silica-and-silica-dust/

Another one from a somewhat more reputable-looking site:

Crystalline silica cat litter is one of the newest types of absorbent litter on the market. It works by absorbing your cats urine and "drying" it eliminating the smell and keeping the litter dry. This type of litter is quite popular due to it's ease of use. However, some health concerns exist. Silica dust contains silica particles and is a known human carcinogen according to the International Agency on Cancer. Breathing in this silica dust may pose a health risk to you and your cat.

Prolonged exposure to crystalline silica dust has been associated with silicosis (a non-cancerous, sometimes fatal lung disease), bronchitis and tuberculosis in humans.

In cats, inhaling the silica dust can cause respiratory infections. If your cat ingests the silica while cleaning its paws, the silica may accumulate in your cat's intestines over a period of time causing health problems. When ingested, the litter will expand and absorb moisture in the intestines preventing the absorption of nutrients as well as cause dehydration and blockages.

https://www.vetinfo.com/silica-cat-litter-toxic.html

The cat litter I bought for our new kitten contains silica sand, it's very convenient as it controls odours and lasts for almost a month before having to replace it.

enter image description here

Is there any truth to silica sand based litter dust being hazardous to human or cat health? I'm assuming clumping clay is just another word for silica sand or is that actually a different type of cat litter, is it true?

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Most "sand" is primarily silica sand. The common tan or beige color is typically caused by a few percent of iron oxides. It is up to you to decide if beach sand or desert sand is too dangerous for your cat : Personally I doubt it would be a problem . Silicosis can be a problem where silica is ground under dry conditions producing airborne dust.

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  • So "silica sand" is just regular beach sand (with silica gel added i presume)? Most dust occurs while cleaning it, i guess i could use a vacuum cleaner to suck up the dust or just wear a mask while cleaning the litter tray. Maybe worth looking for less-fine silica sand that doesn't produce dust when used by the kitten – Jan Vladimir Mostert Feb 9 '19 at 21:24
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Potentially yes it is. For both you and your pet.

What is crystalline silica? Crystalline silica is a basic component of soil, sand, granite, and many other minerals. Quartz is the most common form of crystalline silica. Cristobalite and tridymite are two other forms of crystalline silica. All three forms may become respirable size particles when workers chip, cut, drill, or grind objects that contain crystalline silica.

What are the hazards of crystalline silica? Silica exposure remains a serious threat to nearly 2 million U.S. workers, including more than 100,000 workers in high risk jobs such as abrasive blasting, foundry work, stonecutting, rock drilling, quarry work and tunneling. Crystalline silica has been classified as a human lung carcinogen. Additionally, breathing crystalline silica dust can cause silicosis, which in severe cases can be disabling, or even fatal. The respirable silica dust enters the lungs and causes the formation of scar tissue, thus reducing the lungs’ ability to take in oxygen. There is no cure for silicosis. Since silicosis affects lung function, it makes one more susceptible to lung infections like tuberculosis. In addition, smoking causes lung damage and adds to the damage caused by breathing silica dust.

Source: osha.gov

See this related question for other options What are the advantages and disadvantages to using a safflower seed litter box with my rabbit?

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While many sites cite "claims," I have so far only found one actual scientific study of whether silica particles from cat litter and respiratory disease in cats are linked, which concluded "maybe."

Interpretive Summary

Inhaled silica dust has been implicated as a cause of lung cancer and other respiratory diseases in humans and several animal species. Electron microscopy and x-ray spectroscopy were used to identify and characterize dust particles from seven brands of commercially available clay cat litters and to identify, characterize and quantify particles in the lung wash fluid of six cats with and six cats without signs of respiratory disease. Dust particles from clay cat litter have an identifiable appearance and elemental ratio (primarily aluminum and silica) and the same pattern was observed in particles obtained from lung wash fluid. Significantly more silica particles were obtained from cats with than without respiratory disease. This suggests an association between presence of silica particles and respiratory disease, but it is unknown whether silica dust particles contribute to respiratory disease or accumulate because of interference with normal lung ciliary function.

Detection of Silica Particles in Lung Wash Fluid From Cats With and Without Respiratory Disease (Emphasis mine)

While there may not be definitive proof at this time as to whether or not silica dust specifically from cat litter is harmful to you or your cat, there exists a much broader range of studies demonstrating the risk of silica dust in general.

You also mentioned "clumping clay," which is sodium bentonite. It absorbs moisture very well, but if your cat tends to get litter stuck to its fur and lick it off, it could cause issues different from the inhalation risks of the silica dust.

Should you wish to avoid silica clay, a wealth of alternative litters currently exist, using materials such as wood (chips/shavings/dust), paper, and plant products (corn, wheat, nut shells). A column on Scientific American lists a number of these products by brand name.

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I think answering this complicated and interesting question might be difficult. But I did some research and I'm going to provide my insight despite the fact that great answers already exist there. I want it to serve as a follow-up supplement to existing answers. I just think it's really important subject for anyone concerned.

At first I am going to confirm that yes, silica sand is just a formal term for naming ordinary, common sand you can find for example in sandboxes located on the children's playground and on beaches of non-tropical coastlines. It is exactly the thing that comes to mind of most people as first after hearing the word "sand", and silica is chemical name of the main constitutent of this type of sand. Silica and silica sand are inert substances, commonly occur in nature and are chemically non-toxic upon oral digestion.

On the other hand, it is also true that inhaling finely divided silica particles is a significant health hazard: especially if silica is in its crystalline form - which is the case in silica sand - it is known for causing serious disorder which you've mentioned, including lung cancer.

But it's not like silica is inherently dangerous itself.

Actually, it's generally just dangerous and unhealthy for us to inhale finely divided particulate matter because it interferes with one's respiratory system, in particular with the lungs. Inhaling fine particles of many other common, normally harmless substances like, for example, flour, coal or cotton also causes wide range of respiratory diseases generally refered to as pneumoconioses.

Danger depends on the size of these respirable particles: relatively large particles (around 10 micrometers and bigger) are less dangerous because they don't make their way to the lungs - instead, they get stopped and deposited in upper respiratory tract where they aren't nearly as damaging, but smaller particles (less than 1 micrometer in size) go deep down into the lungs and wreak havoc within the alveoli. On the photo you've provided in your question I could see a writing on the litter package that says "this product is super fine" which, if refers to sand particle size, may be concerning in this context.

However as far as I could find, disorders related to inhaling silica dust are mostly known for being occupational diseases affecting construction site workers, miners and generally people working in industrial setups involving stonecutting and stonegrinding so I don't think that conditions during daily cat litter handling are exactly comparable.

Non-occupational forms of these diseases were also reported due to enviromental exposure and dubbed as desert dust pneumonia, but I still don't think these conditions are comparable to this concern with cat litter, unless the litter tends to raise visible clouds of dust during handling.

Also, I'm really sceptic about the claim of silica particles pontentially accumulating in cat's intestines over extended period of time. Small ingested amounts should inertly pass through I think. As long as there particles stay out of respiratory system they are at most capable only of causing minor irritation.

So in principle it could be dangerous, but the answer depends on many variables. In conclusion, one couldn't really be absolutely sure before checking this particular brand of litter and examining it under the microscope.

As for sources, my general source was Wikipedia.

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