I would add that over time as the window is opened and closed lead dust can build up on the sills and baseboards as it is worn down through use.

When I was with early intervention we recommended peopke wash sills and baseboards with a cleaning solution high in phosphates, such as Spic N Span or automatic dishwasher powdered soap. You mix ¼ cup to 1 gallon warm water, and wear rubber gloves while cleaning. Wipe surfaces with the phosphate solution, then rinse with clean water. Change water in buckets for each room or as necessary, and pour water down toilet.