Living in the land of sushi, it might seem strange that I don’t eat sushi that often. I doubt I make it out to sushi even once a month. Maybe once every other month.
Don’t get me wrong, I love sushi, but generally speaking I don’t eat cheap sushi. If I’m not interested in paying a lot of money for a meal, there are so many other good things to eat here in Japan. And generally speaking, cheap sushi isn’t good.
The NY Times has a good article on the usage of carbon monoxide to preserve raw fish. This is why cheap sushi is just not worth your time and money.

The global seafood trade has expanded so much over the last decade that tuna, once a seasonal delicacy, is available year-round. But getting it to consumers while it still looks fresh is difficult. Tuna quickly turns an unappetizing brown (or chocolate, as it is called in the industry), whether it is fresh or conventionally frozen and thawed.
Carbon monoxide, a gas that is also a component of wood smoke, prevents the flesh from discoloring. It can even turn chocolate tuna red, according to some who have seen the process.
People in the seafood industry estimate that 25 million pounds of treated tuna, about 30 percent of total tuna imports, were brought into the United States last year, mostly from processors in Southeast Asia. Retailers in the United States buy it already treated.
The Food and Drug Administration says the process is harmless. But Japan, Canada and the countries of the European Union have banned the practice because of fears that it could be used to mask spoiled fish.

Now I’m less and less inclined to eat sushi in the US, knowing that most places are serving Southeast Asian carbon-monoxide treated tuna, not the good stuff that we see coming out of Tsukiji Market in Tokyo.
Americans are being exposed to raw fish that is unworthy of Japan and the EU. People will get sick and blame sushi itself, not cheap producers who cut corners and use carbon-monoxide hide bad colored fish. It’s a lose-lose for all involved except the fish retailers.
Tuna’s Red Glare? It Could Be Carbon Monoxide [GoUpstate.com]