The difference between green and black tea, by the way, is based on the degree of oxidation the leaves receive.

Green tea comes from leaves that are steamed, pan-fired, or oven-fired immediately after picking, so minimal oxidation occurs. (White tea, made from new-growth buds and young leaves, is even less processed.)

In a black tea—or red tea, as it’s called in China—the leaves are well and truly oxidized.

The type of tea called oolong occupies the middle range; its partial oxidation results in varying, distinctive flavors and complex aromas.

http://www.takepart.com/article/2013/06/12/green-tea-lead-soy-lecithin?cmpid=foodinc-fb

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All teas are rich in antioxidants, but green tea, especially when brewed from loose leaves, is known for its great abundance of the polyphenols classified as catechins—in particular, epigallocatechin-3-gallate (EGCG). A great deal has been written about the health benefits of green tea, so I’ll spare you here; for an in-depth review, check out this research from the University of Granada, in Spain.

Okay, about this lead business. ConsumerLab.com, an independent site that tests health and nutrition products, reported on May 21 that not only did catechin and caffeine levels vary widely in the green teas it tested (from Bigelow, Celestial Seasonings, Lipton, Salada, and Teavana), but that some contain lead in their leaves. “Lead is known to be taken up into tea leaves from the environment and can occur in high amounts in tea plants grown near industrial areas and active roadways, such as in certain areas in China .... the liquid portions of the brewed teas [italics mine] did not contain measurable amounts of lead (i.e., no more than 1.25 mcg per serving).”

A microgram is equal to one millionth of a gram. As long as you don’t eat the tea leaves, you have nothing to worry about, in other words.

That said, limiting our exposure to lead is a smart thing to do (for excellent in-depth reporting on the subject, read USA Today’s recent coverage), but it’s important to understand that the chemical element occurs naturally everywhere, even in uncontaminated soils. Fortunately, a healthy diet rich in vitamin C, calcium, and iron can help mitigate lead’s harmful effects.

Lead contamination of C. sinensis has been studied at the Chinese Academy of Agricultural Sciences, in Hangzhou, for years. In one article, published in the January 2006 issue of the journal Environmental Pollution, Chinese researchers analyze the lead concentrations in 1225 tea samples collected nationally between 1999 and 2001; among their findings was that 32 percent of the samples exceeded the national maximum permissible concentration and there was an increasing trend in tea lead concentration from 1989 to 2000. In another, more heartening piece, published the following year in the journal Chemosphere, the researchers indicate that the liming (neutralizing) of acidic tea-garden soils is an effective way to reduce lead contamination in tea leaves.

And, you may ask, what about trace amounts of radiation showing up in Japanese green tea? Much of that country’s tea is produced far to the west of Fuskushima, where the 2011 nuclear power-plant disaster occurred, but still—is there reason to worry? I turned to Elizabeth Andoh, the world’s leading English-language authority on Japanese food (and longtime Gourmet contributing editor). “The subject of radiation contamination of the food chain (tea included) is VERY complicated,” she wrote. “For me, the bottom line is the reputation of the vendor and the vendor's diligence in researching and testing.” If choosing an online vendor, look to see if the company includes radiation test results for their teas.

So, should you simply avoid green tea altogether? Well, it’s not a necessary nutrient, so it is your choice to drink it or not. Jeffrey Blumberg, director of the Antioxidants Research Laboratory and professor at the Friedman School of Nutrition Science and Policy, both at Tufts University, weighed in. “The vast majority of observational studies on large populations of tea drinkers (including those in China) show a dose-related health benefit of tea consumption (i.e., the larger the intake, the greater the benefit), particularly in reducing the risk of cardiovascular disease,” he wrote. That’s enough for me.
Tips for buying and brewing green tea
When buying green tea, it’s worth remembering that it is an agricultural crop. Its quality from year to year depends on a number of factors, including climate, weather, soil health, proximity to highway or industrial pollutants, whether it’s harvested by hand or machine, and the care with which it’s been handled, stored, and shipped. “There are thousands of green teas in China,” explained tea merchant Sebastian Beckworth, who travels to remote parts of that and other countries to source fine teas from small farms and collectives. “I don’t blend my teas for consistency,” he added. “I’d rather find farmers who are making a good crop and buy it. And when it’s gone, it’s gone.”
He also introduced the concept of seasonality. “The harvest time is now,” he said. “And green teas don’t keep as long as black teas do. Enjoy a green tea for six months, then try something else.” Any other tips? Forgo prepackaged teabags, which are filled with bits of broken leaves, for the loose leaves; in general, they’re of higher quality, fresher, and you’ll be rewarded with nuances of flavor. And because green tea is so delicate, always brew the leaves in water that hasn’t quite reached a boil (about 180 ºF).