Hello to wife of Jack. I'm sorry you lost your husband and had to go through this with his MDS. Yes, several toxins and prior chemo certainly are known to cause MDS. The incidence also rises with age (also diabetes and heart disease). But I don't think that most cases are caused by environmental factors. While there is a great deal of research going on, most cases have no known cause. Here is a link to cancer.org that addresses this issue.:
http://www.cancer.org/cancer/myelody...es-what-causes
Some things just happen! I choose not to focus on the "why", but rather on the "living". Certainly those who were exposed to the known toxins have a better idea of the cause of their MDS.