One thought would be to consider using Logback, which has a better api for this sort of thing.  Something along the lines of:
logger.debug("LanguageMismatch - ptld: {}, Lang: {}, staffId: {}", $pd.participant.id, $ptLanuage, $nd.staffId);

That buys you conditional logging without requiring the performance hit of assembling a string unless logging is enabled for the statement.