This NY Times piece reports on the current scientific understanding that babies actually need to ingest the dirt in their environment (with germs and worms and all those goodies) to help train and instruct their nascent immune system to function properly, and lack of that training leads to increased autoimmune diseases (and possibly other immune deficiencies as well?)
http://www.nytimes.com/2009/01/27/health/27brod.html?em

What the scientists fail to take into account, though, is that today's environment is no longer safe for such evolutionarily developed, health-sustaining instincts. The dust that settles around us today is full of toxic chemicals that are released from coal-fired power plants, municipal waste incinerators, petrochemical industries, mining sites, fossil fuel burning vehecles, including international shipping, commercial and military jets, artillery shells and missiles from wars fought on distant continents, rockets, crude electronic waste recycling sweatshops, etc. etc.

Every one of the hundreds of Americans tested were found to have a whole host of synthetic, toxic and carcinogenic chemicals in their blood[1], such as flame retardents, plasticisers, teflon chemicals, and pesticides/herbicides, with younger children showing the highest amounts, presumably due to their proximity to the ground where dust settles and are stirred up and inhaled, and due to small children's habit of putting everything into their mouths.

Putting these two threads together, it is clear that we must stop the insanity of toxic release and systematic distruction of our environment, the only one our bodies (and other species) have evolved to know how to live in. Tens of thousands of synthetic chemicals are callously produced and released, and each year thousands more new chemicals are put on the market. These chemicals are allowed to be released because our laws, even in the most stringent countries, require only that a substnace be prevented from use AFTER it is unambiguously shown to be toxic/harmful. The burden of proof has always been placed on the scientific/medical community to demonstrate (generally taking decades) that substance X causes adverse health effects, which must be teased apart from the effects of a whole bunch of other substances/factors A, B, C...Y, Z that all individually require such proof. And even when proof is rock solid, the "lack of suitable replacement" is used as legitimate reason for delaying the removal of a substance from the market. Many such substances are persistent in the environment due to their chemical stability and lack of biodegradation (no surprise, what crazy organism would have evolved the ability to make use of such substances that didn't exist before we came along?), and many are bio-accumulative due to their fat solubility, thereby concentratng up the food chain.

The collective intelligence of our species must, MUST, overcome the lobbying forces driven by greed and shortsighted pursuit of profit by polluting industries (and you may be a shareholder!), to change the fundamental paradigm of how we allow experimentation with our chemical and physical environment. This is literally for the survival and well-being of all our children, rich or poor. Precautionary principle must be adopted on all environmental fronts, and the burden of proof must be placed on proponents of any chemical entity, or physical device (such as wireless communication devices), to show that they are, beyond reasonable doubt, safe. This shift will not happen unless our voice is louder than corporate lobbyists', and that requires that you, and everyone you know, to make your voices heard.

[1] See reports on body burden of toxic chemicals, on the Environmental Working Group website: ewg.org