Note to users. If you're seeing this message, it means that your browser cannot find this page's style/presentation instructions -- or possibly that you are using a browser that does not support current Web standards. Find out more about why this message is appearing, and what you can do to make your experience of our site the best it can be.
HERTFORDSHIRE, U.K.--One big unknown on the health front is whether long-term exposure to ash and gases gives rise to chronic illnesses, a question now being tackled in earnest.