In New Hampshire, researchers at Keene University are studying the toxicology of biodiesel particulates. The team mounted particle impactors in the operator’s cabs in machinery at the Center, collecting samples of both petroleum diesel and biodiesel exhaust. The impactors can separate out different sizes of extremely tiny particles, which lets the researchers see exactly what the drivers are breathing. They found that although the amount of particulates in biodiesel exhaust is indeed lower than those from petroleum diesel, their chemical composition is different, which raised another question: Though there are fewer particulates in biodiesel exhaust, what if those particulates are more toxic than their petroleum-based counterparts? If so, that has implications for human health.