It's been more than one week since Japan started releasing nuclear-contaminated water into the Pacific Ocean. It's the first of a four-round discharge as part of a plan to dump more than 1.3 million tons of water from the wrecked Fukushima power plant into the sea over the next 30 years. Though Japan insists the water is "safe," the move has triggered strong responses, including bans on Japanese seafood imports. How can we evaluate the short- and long-term effects of nuclear contaminants? What could be the risks to nearby countries? And are their requests for compensation justified?