Environmentalist around the U.S. recognized Earth Day, Thursday, to raise awareness about ecological issues like pollution and energy waste.
Many Christians don't observe the day because of concerns that some people take "going green" too far and actually worship the earth.
Matthew Sleeth, author of The Gospel According to the Earth, says it's possible to be a Christian and an environmentalist -- as long as everything is kept in proper perspective.
"For me, it's always been that creation has a Creator and the creation glorifies the Creator," he explained. "God and Christ are at the center of everything we do, whether we're gardening or going out to dinner."
"So as long as we keep our eyes on the Creator, on Christ and the Bible, we're okay," Sleeth continued. "We're theologically sound. "
He added that Christians have a responsibility to be good stewards of the earth and that one of the added benefits is saving money.
The first Earth Day was held in 1970, when smog reached choking levels in states like California.
Researchers say pollution is still a concern today, but not as bad. Smog levels nationwide have dropped by 25 percent and lead levels in the air have reduced more than 90 percent.
Still, environmentalists warn that issues like climate change remain.
"We've cleaned up what you can see and left everything else in limbo," said Kathleen Rogers, president of the Earth Day Network.
According to the National Oceanic and Atmospheric Administration, carbon dioxide levels in the air have increased 19 percent and the western U.S. still has 6,000 yearly premature deaths linked to unseen tiny particles in the air that cause heart and lung problems.
*Originally aired on April 22, 2010.