I have a situation where our client is very concerned that GWB with recycled content needs to be specially sealed in order to maintain a healthy environment. Because of this concern, we have been asked not to use recycled content GWB and to use conventional GWB "because it is healthier". Two questions: 1) is this concern valid? (or is it simply based on the sulfurous GWB imported from China several years ago); 2) is a special, additional sealer coat needed for recycled content GWB (Kilz, etc.)?