Hillary Clinton's 10-point win over Barack Obama in the Pennsylvania primary means the U.S. still doesn't have a strong enough frontrunner for the Democratic nomination and almost assures more infighting between the two candidates instead of constructive talk on climate change. Now, what started as a dynamic race for the presidential nomination between two stellar choices now just makes me weary.

The Democratic National Convention in August can't come soon enough, especially in light of a new review from the National Sciences Academy (NAS) describing a clear link between ozone pollution and premature death:

Ozone, a key component of smog, can cause respiratory problems and other health effects. In addition, evidence of a relationship between short-term -- less than 24 hours -- exposure to ozone and mortality has been mounting, but interpretations of the evidence have differed, prompting EPA to request the Research Council report. In particular, the agency asked the committee to analyze the ozone-mortality link and assess methods for assigning a monetary value to lives saved for the health-benefits assessments.

Based on a review of recent research, the committee found that deaths related to ozone exposure are more likely among individuals with pre-existing diseases and other factors that could increase their susceptibility. However, premature deaths are not limited to people who are already within a few days of dying. -- NAS press release

This NAS review outright refutes the current White House stance that no solid connection exists between smog and fatal lung issues, a position that affects the clean air regulations in this country:

Vickie Patton, deputy general counsel for the Environmental Defense Fund, said the Academy's findings "refutes the White House skepticism and denial" of a proven link between acute ozone exposure and premature deaths. Such arguments have been used to diminish the health benefits of reducing air pollution, she said. -- CNN.com

Yet the continuing tight race between Clinton and Obama will likely bring more comparisons of electability and experience, less focus on how either one plans to undo the eight-year "Climate change? What climate change?" policy of the Bush administration.

According to the newest League of Conservation Voters’ National Environmental Scorecard, both candidates have respectable voting histories on eco issues. Presumptive Republican nominee John McCain? Not so much.

While all three experienced drops in their previous scores because of campaign-induced absenteeism, Clinton sits at 73 out of a possible 100 and Obama at 67. However,

[B]oth made a point of being on hand for the key vote that would have allowed a version of the energy bill to move forward that included a provision to repeal billions of dollars in tax breaks for big oil and put that money toward clean energy programs. -- LCV press release

John McCain, on the other hand, scored a big, fat zero.

Yes, that’s zero.

It’s an interesting number, considering he positioned himself as the environmental Republican candidate earlier this year in New Hampshire:

"I will clean up the planet," McCain said. "I will make global warming a priority."

McCain often says that he wants to reduce dependence on foreign oil and that he wants to increase the use of nuclear power. His usual line is that these efforts also will help reduce global warming. But yesterday, appearing before a crowd of several hundred in this relatively liberal city, he focused solely on the environmental argument. He didn't mention nuclear power. He was appealing directly to the state's sizable environmental community, which includes many independent voters who are taking one last, close look at McCain. -- Michael Kranish, Boston Globe

McCain is known for his straight talk, but last year’s LCV score tells a different story. He managed to miss every one of the 15 votes on environmental issues in Congress last year, including that big one on eliminating massive tax breaks for oil companies, a measure that failed by only one vote.

One vote. Think about that for a minute.

Next up, Clinton and Obama are facing primaries in North Carolina and Indiana, neither of which are expected to break the tight race between them. Meanwhile, McCain greenwashes and Democrats watch, and wait.