This is a cluster randomized crossover intervention. We will conduct this study for 9 days and each experimental step lasts for 3 days. We randomly assign one building with 8 appropriate study subjects to a serial of control-intervention-intervention steps and another building with also 8 appropriate study subjects to a serial of control-control-intervention steps. Intervention step means study subjects will carry one big bag containing two stainless containers, one stainless spoon, and one stainless chopstick and use them for each meal during the trial (Some subjects will need to take pictures randomly and email back before the meal). Control means study subjects will carry one big bag without those stainless container, spoon, and chopstick and only use the containers provided by vendors for each meal during the trial (Some subjects will need to take pictures randomly and email back before the meal to check their adherence). Collect 24-hr urine samples for 9 days for melamine levels.