Butadiene and its 2-methyl analog, isoprene, are important chemicals,
extensively studied in animals and in worker cohorts. This symposium,
building on previous conferences and substantial additional metabolic
and epidemiologic data, brought together leading scientists from indus
try and academia and knowledgeable regulators to address the complex t
ask of assessing likelihood and magnitude of risk to humans and approp
riately protective standards for occupational and general environmenta
l exposures. These agents and these discussions are an excellent case
study for general challenges in risk assessment and risk management.