Many conventional insulation materials off-gas VOC’s, toxic chemicals like formaldehyde and HCFCs that affect health or the ozone, or are made from petrochemicals.  See our Article Indoor Air Quality -- Identifying Sources and Making Renovation Choices that Eliminate Contamination.  There are new products on the market for loose fill, blown-in and blanket and batt insulation that are made from sustainable or renewable sources such as cellulose, recycled cotton and soy, are not derived from petrochemicals and that do not off-gas VOCs, even new fiberglass products that do not contain formaldehyde are available, so there really is no reason to have to settle for an unhealthy or otherwise environmentally challenged product.  The Green Home Guide has prepared The Green Buyers Guide to Insulation which is a helpful summary of insulation products, and comparative pros and cons including health issues.