It depends who you ask. My answer is YES.
I would strongly suggest you get them to vacuum it up and stop cutting the siding in an area where the dust cannot be collected well. They should cut using a vacuum attached to the saw. Don't be soft about it. Let them think you are crazy. They will be long gone and you won't see them again. But the PVC dust will stay with you.
PVC (aka vinyl) is all around us. Shrink wrap, plastic, car seats, food containers, etc. So it is not that the dust will kill you. But it will add to the toxic cloud you live in. Without doing anything but living a Western life you are surrounded by thousands of chemicals on a daily basis.Just look at your desk and you will see countless examples of chemicals, among them PVC.
I believe this is why we have a cancer epidemic, neurological issues (ADD, OCD, depression, etc.), and many other illnesses. Our bodies are bombarded by chemical stressors that beat down our health over time.So the idea is to lessen your exposure by getting at the low-hanging fruit.
You may not be able to stop your exposure to the hundreds of chemicals in your car. But you can certainly get off your butt and tell those workers to stop making a mess and to clean up the mess they have already made.
While you are at it, give them an earful on how PVC makes them infertile. That will get their attention.
Quote from research done by TurnerToys.com*:
PVC contains Phthalates, which accumulate in body tissues, can damage liver, lungs, and have been shown in lower mammals to damage reproductive organs. Phthalates are freely given off by plastics in which they occur, and because they are fat-soluble, Phthalates are found in quantity in meats and cheeses wrapped in PVC packaging. Although Phthalates show almost no toxicity in adult humans in acute (short-term) doses, even at high doses, the cumulative nature of Phthalate toxicity results in toxic effects when ingested chronically (over a long period of time), even at very low dosage. Very young infants do not metabolize Phthalates as well as adults, and so are at greater risk of harm. The common availability of Phthalates in the consumer environment causes inevitable chronic ingestion for almost all modern industrial consumers.
* copyright 1998-1999 18th Century Industries, Inc.