Integration of Environmental Management Systems, (EMS) and Occupational Health and Safety Management Systems (OHSMS) into an EHSMS (Environmental Health and Safety Management System) is the way to go. ISO 14001:2004, OHSAS 2007 are your best choices for models of continual improvement management systems that are easily integrated. Both of these standards share many common elements and integration avoided the confusion of having separate process that address these in the EMS and OHSMS.
Separating the results of environmental aspect identification required by ISO 14001 and the hazard identification and risk assessment required by OHSAS 18001 alos helps avoid confusion. Get some help from an experienced, competent professional when you are deciding how to identify aspects and evaluate hazards and risks. If this part of the EHSMS implementation process is not done with skill, the effectiveness of the EHSMS will be greatly compromised.
Here is a link to a brief discussion about approaches to OHSMS hazard identification and risk assessment.