Information on this topic. Although, not directly related to 3D printing, it does address some research on styrene toxicity.
Thanks for moving this here Larry 
From the National Institutes of Health - NIH);
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Subsequent epidemiologic studies found styrene workers had increased mortality or incidences of lymphohematopoietic cancers (leukaemia or lymphoma or all), with suggestive evidence for pancreatic and esophageal tumours. No adequate human studies are available for styrene-7,8-oxide although this is the primary and active epoxide metabolite of styrene. Both are genotoxic and form DNA adducts in humans.
Hence, based on both animal and human cancer studies and genotoxic findings including clastogenicity and DNA damage in workers as well as on other supportive and biologically plausible mechanistic results, styrene and styrene-7,8-oxide should be considered as presenting carcinogenic risks to humans, particularly for lymphatic/hematopoietic cancers.
As mentioned before, it’s not just the toxic chemicals that can be a health issue, it’s also their size (less than 100 **nanometers**). They are classified as UFPs (ultrafine particles). When inhaled, UFPs get trapped in the lung’s alveoli. UFPs are small enough to then pass directly from the lungs and be deposited into the bloodstream, where they accumulate in other organs of the body such as the brain, the liver, and the spleen. If you’re interested in the science behind all of this, there is a good article posted at Environmental Science and Technology here;
http://pubs.acs.org/doi/full/10.1021/acs.est.5b04983
And it’s not just about the Styrene per sa, it’s about what chemically happens to the Styrene when it is heated to high tempertures by the printhead. Also, Styrene is just one of many toxic chemicals that make up 3D printer filament. As a precaution I have ordered a RZ mask (https://rzmask.com) and will be enclosing my 3D printer, which will then be vented to the outside with a bilge pump. I also understand that not everyone takes health issues like this as seriously as I may, but hey, I really do LOVE my X-Carve, and want to increase the chances of being able to use it for many years to come 
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