Read the following passage and answer the question that follows.
'The New Jersey Department of Environmental Protection (NJDEP) has issued new guidelines concerning the disposal of electronic waste, or 'e-waste.' Effective immediately, all state agencies are required to use only certified e-waste recycling vendors.
This policy aims to prevent hazardous materials, such as lead and mercury, from contaminating landfills and groundwater.
A list of certified vendors is available on the NJDEP website.
Agencies must document all e-waste disposals and submit a quarterly report to the Office of Sustainability.
Failure to comply will result in a formal review and potential penalties.
This directive supersedes all previous memoranda on the subject.'
What is the primary purpose of this new directive?