Silica + pesticides

[flowergirl]

Hello, I am not knowledgeable about chemistry whatsoever, but I run a company preserving bouquets out of my home and I have some questions about the silica that I use to dry flowers. 
I use a brand called Activa silica gel which has a fine grain sand texture. I pour the silica over flowers in order to absorb the moisture out, and then pour it off of the flowers and bake the silica in the oven again to dry out, or reactivate the silica. 

It's well known that flowers can have up to a dozen different pesticides by the time they make it to the shelf. I currently work with a face mask because it kind of freaks me out to breath in the silica dust that gets kicks up with a lot of use and probably stores some of the pesticides.

Essentially, though, I'm concerned that the silica is absorbing pesticides from the flowers and potentially causing harm both to myself and my roommate while it's heated in the oven. 
The silica itself is labeled as non-toxic, but the product advises you not to reuse any of the plastic containers in which you've used the silica because the pesticides in the flowers can absorb permanently into the plastic and cause harm.

Could this same principle apply to my oven, or can anyone offer any insight into how pesticides might react under this kind of heat (250F for 4-5hrs)? Is a kind of gaseous effect possible for the pesticides when the silica is kicked up as dust or when evaporating with the moisture in the silica? Could the pesticides absorb into the oven and hang out there permanently? Any idea on the science behind whether it would help for me to regularly manually clean the oven or use the self-clean option using much higher temperatures? 

I'm absolutely not asking for medical advice, and maybe this isn't even the forum to ask this kind of question, but any input is so so appreciated! My roommate and I both have health issues so I am really trying to take every opportunity I can to learn more about how these things work and maintain a ~nontoxic~ space. Thank you. :)

[John Cuthber]

Pesticides are chosen to have low human toxicity.

There's unlikely to be enough to be worth worrying about.

[Sensei]

21 minutes ago, John Cuthber said:

Pesticides are chosen to have low human toxicity.

...if they are used according to manual, i.e. used at normal temperatures..

Compounds (especially complex organic compounds) heated in oven to couple hundred degrees will decompose to smaller unknown compounds, and eventually get into random reactions with other compounds around them (e.g. other pesticides or by-products of decomposition etc.), and product of reaction might be eventually harmful.

9 hours ago, flowergirl said:

Could this same principle apply to my oven, or can anyone offer any insight into how pesticides might react under this kind of heat (250F for 4-5hrs)? Is a kind of gaseous effect possible for the pesticides when the silica is kicked up as dust or when evaporating with the moisture in the silica? Could the pesticides absorb into the oven and hang out there permanently? Any idea on the science behind whether it would help for me to regularly manually clean the oven or use the self-clean option using much higher temperatures? 

..do not use this oven for anything but heating your silica gel.. I would not bake cake in it for sure..

https://en.wikipedia.org/wiki/Thermal_decomposition

e.g. thermal decomposition of sodium bicarbonate (aka "baking soda") is responsible for growth of cake during baking.

https://en.wikipedia.org/wiki/Sodium_bicarbonate

Here is (incomplete) list of pesticides with chemical formulas:

https://en.wikipedia.org/wiki/Index_of_pesticide_articles

To tell what will be result of thermal decomposition of some pesticide we would have to know its name for a start.

There are a few scientific articles of thermal decomposition of pesticides:

https://www.google.com/search?q=thermal+decomposition+of+pesticides

e.g. "Pesticides containing a benzimidazolyl group plus one or two linear chains experience multiple stages of thermal degradation between 120 and 650 °C."

9 hours ago, flowergirl said:

Essentially, though, I'm concerned that the silica is absorbing pesticides from the flowers and potentially causing harm both to myself and my roommate while it's heated in the oven. 

If some pesticides etc. was absorbed by silica gel, it will have amount counted in e.g. micro grams, or milligrams, at most.

i.e. several years of drinking and smoking cigarettes will have much higher influence on your health. During smoking of cigarettes compounds thermal decompose to carcinogenic intermediate compounds, which person inhale, and they damage lung cells in a random way.

[John Cuthber]

2 hours ago, Sensei said:

Compounds (especially complex organic compounds) heated in oven to couple hundred degrees will decompose to smaller unknown compounds, and eventually get into random reactions with other compounds around them (e.g. other pesticides or by-products of decomposition etc.), and product of reaction might be eventually harmful.

The toxicologists take this into account.

It is called "cooking".

[Veritas_C&E]

I think you should worry more about breathing in fine silica dust than about the possible minute amounts of pesticide degradation products that may subside after the oven treatment.

Since SiO2 has extremely low solubility it stays in the lungs for years or decades and it is known that breathing in silicate dusts increases the risk of developing lung cancer in the long term (as is the case for breathing in many similar compounds, such as asbestos).

[MigL]

A lot of the more dangerous pesticides are Organophosphates, and are Cholinesterase inhibitors ( think milder forms of nerve gas ).
Very mild exposures have a half life of about two weeks, more extreme exposures can damage internal organs like kidney, or other damage.
Only Nerve gas will result in immediate death.
Some pesticides are actually meant to be applied to humans, but keep in mind that there are other types of pesticides.

https://www.headlice.org/comb/what-are-head-lice-and-nits/chemical-concerns/signs-and-symptoms-of-pesticide-poisoning/

One of the first symptoms of extreme poisoning is very constricted pupils ( along with vomiting ), but in your process you shouldn't even have mild exposure to the pesticide aspects.
You might, however, want to invest in an external vented oven for re-drying your silica gel, if at all concerned.

Edited July 9, 2020 by MigL