I reached out to Mayor Fulop and he very quickly provided some answers from the MUA....

Turns out the culprit is Styrene.

From the MUA...
Styrene is present in the resin used to impregnate the CIPP liners. The styrene levels encountered are at extreme low levels, levels that are many, many times below any possible health effect concern level.

At times, the smell mitigates downstream or upstream of the work site and can sneak into house traps. The contractor uses exhaust fans to help extract the smells outside of the sewers and prevent from migrating.

They provided a PDF which I am not able to attach here but very similar to the this https://styrene.org/faq-styrene/

I would also add the CDCs fact sheet:
https://www.cdc.gov/biomonitoring/Styrene_FactSheet.html

Does anyone know what chemical is being used for the sewer work in Hamilton Park? Do we know it is safe?

The poisonous smell is really bad when you are anywhere near the work being done. Most alarming was the very strong chemical smell coming through our open windows last night as we were trying to sleep. Can't help but feel like we are being poisoned here.