This article in the January 2008 issue of Discovery magazine says that many pollutants act like estrogen in the body. These estrogen-mimicing chemicals skew the gender ratio of newborn babies. Decades past, we saw 51.5 baby boys for every 48.5 baby girls. Over the last few decades, the ratio has changed in many places. For example, in northern Canada, the ratio is 46 boys to 54 girls. In parts of northern Russia, the ratio is very skewed: 30 boys for every 70 girls. In Japan and the US, we now see fewer baby boys born per 10,000 births than we saw years ago. If you check this Wikipedia page, you will see that many of the countries affected are those in former Soviet Union or Eastern European countries which had few if any environmental regulations. Also, several northern countries are affected because the pollutants drift northwards where they accumulate in the environment there. The pollutants also affect the male babies by reducing testicle size and fertility.