Your "guess" that the room or house contains lead would not be sufficient grounds to unilaterally terminate the lease early. You would need to have to the place tested for the presence of lead to confirm whether your speculation is true, and even if so, your remedies normally would be for the landlord to remedy the situation rather than terminating the lease.
Frank W. Chen has been licensed to practice law in California since 1988. The information presented here is general in nature and is not intended, nor should be construed, as legal advice for a particular case. This Avvo.com posting does not create any attorney-client relationship with the author. For specific advice about your particular situation, please consult with your own attorney.
I agree with counsel that mere nondisclosure is not a get out of lease free ticket. If you have sincere concerns, then get it tested. Good Luck.
Please note that this answer does not constitute legal advice, and should not be relied on, as each situation is fact specific, and it is not possible to evaluate a legal problem without a comprehensive consultation and review of all the facts and court pleadings filed in the case. This answer does not create an attorney-client relationship.