While Lavoisier is commonly known for his contributions to the sciences, he also dedicated a significant portion of his fortune and work toward benefitting the public. Lavoisier was a humanitarian—he cared deeply about the people in his country and often concerned himself with improving the livelihood of the population by agriculture, industry, and the sciences. The first instance of this occurred in 1765, when he submitted an essay on improving urban street lighting to the French Academy of Sciences.
Three years later in 1768, he focused on a new project to design an aqueduct. The goal was to bring water from the river Yvette into Paris so that the citizens could have clean drinking water. But, since the construction never commenced, he instead turned his focus to purifying the water from the Seine. This was the project that interested Lavoisier in the chemistry of water and public sanitation duties.
Additionally, he was interested in air quality and spent some time studying the health risks associated with gunpowder's effect on the air. In 1772, he performed a study on how to reconstruct the Hôtel-Dieu hospital, after it had been damaged by fire, in a way that would allow proper ventilation and clean air throughout.
At the time, the prisons in Paris were known to be largely unlivable and the prisoners' treatment inhumane. Lavoisier took part in investigations in 1780 (and again in 1791) on the hygiene in prisons and had made suggestions to improve living conditions, suggestions which were largely ignored.
Once a part of the Academy, Lavoisier also held his own competitions to push the direction of research towards bettering the public and his own work.