According to a study conducted in the U.K., dangerous levels of heavy metal contamination were found in most European red and white wines. Bernard Weiss, PhD, professor of environmental medicine at the University of Rochester, N.Y., expressed concern over the finding of manganese in the wine, citing a connection between manganese accumulation in the brain to Parkinson's Disease.
Responding to the Chemistry Journal report were other members of the scientific community who were skeptical of the findings.
Information absolutely required by the ATF (Bureau of Alcohol, Tobacco and Firearms that regulates the wine industry) on American wine labels is alcohol content and net volume. There are 3 other bits of information that fall under "minimum requirements," brand, designation (or class or type), and location of origin. However, the USDA restricts the addition of sulfur dioxide to "organic" wines during the winemaking process, and the mention of sulfites on the label of non-organic wine, as an allergen alert (in New Zealand and Australia since 2002), is dependant upon the level of sulfites.
Because sulfur dioxide is a natural byproduct of fermentation, no wine is 100% sulfite free. In the U.S., the U.S.D.A. forbids producers from adding sulfites to wine labeled “organic,” although the wine may contain as much as 100 parts per million of naturally occurring (that is, not added) sulfites. In Europe, Australia, New Zealand and Latin America, added sulfites are permitted in organic wine. Like the regulatory bodies in these countries, Appellation Wine and Spirits calls wines organic as long as the producer does not use synthetic chemicals in the vineyard.
Source: Appellation Wine and Spirits
Wine doesn't really have nutritional value like we would think of foods we eat. We don't consume wine for nutritional value.
While I think it's important to be aware of the dangers of heavy metals, sulfites and any otherwise toxic substances in the wines, it's also important to remember that a single glass probably doesn't contain enough to hurt you. It's the excessive consumption that can.