The spray coatings under many sinks are usually designed to help soundproof the sink. They are accoustical insulators.
Although I have no way to verify what it is from your description, it is usually made of some type of high density spray foam or mass-loaded vinyl.In either case, the odor and toxic byproducts usually dissipate quickly.
In the mean time, it could be hazardous to your health should you work around the sink for extended periods of time.
- I'd suggest some serious ventilation such as fans, open windows, and air purifiers.
- I've written a recent post in the Green Home Guide regarding the topic of air purifiers which you can read here.
Identifying the source of the odor
We have sealers for almost every type of toxic odor but we need to know what we are dealing with.
Spray coating. My hunch is that it is not the white stuff underneath the sink because it would have been sprayed in a factory months ago and would not be as intense for this long. Our company takes calls on smelly objects every single day for the past 21 years and we've never heard complaints about this particular problem.
Adhesive/caulk/sealant. The real problem may lie with the adhesive/caulk/sealant used to adhere the sink to the countertop. Often contractors use a product that contains solvents or silicones that smell badly. If that is the case, they are difficult to remove or seal. However, their off-gassing usually does not last too long.
Plumbing adhesive. Another possibility might come from the adhesive used by the plumber to connect the drain to the trap. Often PVC cement is extremely nasty and people complain about this regularly. Again, this rarely lasts long and there are no sealers for this as far as I know.
Removing the sink may reveal the problem as you will be able to get your nose closer to the source.
Once you can isolate the problem, call me and we will try to work out a solution.
For more information:
Read "The underside coating of our stainless steel sink has a strong odor. Is it toxic? What should we do?" a Q&A answered by Molly McCabe.