Epigenetics is the elephant in the room that industrial agriculture and its network of company science doesn't want to think about (it lurks in on synthetic biology too). Epigenetic effects are "usually taken to encompass changes in the genetic material — the genomic DNA and chromatin — that alter gene expression in a manner that is heritable during somatic cell divisions (and sometimes even in germline transmission)" here
No one really knows how it works, but its possible that what your grandmother ate effects some aspect of your phenotype. And corn belt babies may be passing, immune system disorders and sterility to what could be the last generation.
Many studies are indicating that agriculture chemicals, like Atrazine, are creating effects that don't surface initially, but for the next generation.
"In one study, Dr. Winchester says, baby rats exposed to atrazine, an herbicide that is banned in European countries, were born with no birth defects. But they developed problems including infertility, kidney and prostate problems, cancer and shortened lifespans as adults - and passed them on to their offspring.
That means agrichemicals could have effects for generations to come, he says".
This Globe and Mail article Risks of Birth Defects Linked to Month of Conception (when spraying takes place) describes the similar effects between Altrazine and the chemical bisphenol A, "a plastic-making compound able to act like a female hormone. Not only can it disrupt the hormonal systems of living organisms, but it does so at very low doses."
Devinder Sharma is right to question the short-sightedness of scientic studies in gm crops toxicity as well:
"If this is true of pesticides, I wonder how can the Genetic Engineering Approval Committee (GEAC) be satisfied with the so-called long-term tests done by Mahyco on Bt brinjal. The longest toxicity tests, which are for only 90 days, cannot assess long-term effects like the development of tumours or cancers from genetic modification. No safety can be concluded about Bt Brinjal based on this, and considering the above mentioned study on atrazine exposure in rats, it is obvious that the true impact can only be known when research spans for a few generations."
Some scientific study links
Developmental Immunotoxicity of Atrazine in Rodents
Neuroendocrine and behavioral effects of embryonic exposure to endocrine disrupting chemicals in birds