Look at photos of the gigantic udders on rBST treated dairy cows and it’s not hard to imagine the artificial hormone’s role in increasing U.S. rates of breast and prostate cancer, precocious puberty and obesity.
But U.S. milk producers and agricultural officials continue to say Monsanto’s Posilac, which has been used unlabeled in much of the U.S. public milk supply since 1994, is safe. 
Even as they jump all over each other to ban it.
Last year, Oregon’s Tillamook County Creamery Association, the nation’s second largest maker of chunk cheese, renounced rBST. 
This year, Dean Foods and H.P. Hood, New England’s two largest milk processors, Arizona’s Shamrock Farms and Northwestern Dairy Association’s Darigold did. [3, 4]
And Dean Foods in Texas and Prairie Farms Dairy in Carlinville, IL, are leaning in that direction. 
Even Vermont Agriculture Secretary Steve Kerr has come out against rBST as his state moves toward zero tolerance. 
Created by combining cow DNA with E coli, (yes, that E coli) Monsanto’s recombinant bovine somatotropin, rBST, designed to make cows produce more milk, was one of the first genetically modified substances approved for U.S. consumption by the FDA in 1993.
But its Frankenfood roots, hormonal actions, unlabeled status and expediency approach to agriculture–squeezing more profit out of each animal “unit”– earned it the ire of farmers, consumer groups, environmental organizations and animal advocates. Even Mario Cuomo declaimed it when he was New York Governor. 
To this day rBST remains banned in Canada, Japan, the EU, Australia, New Zealand and all but 19, mostly nonindustrialized, countries though Monsanto says that’s because of “an oversupply of dairy products” not safety concerns. 
In fact the more you learn about rBST, the more you wonder why anyone would think it is safe.
Take the unpublished rat study Monsanto supplied to the FDA for drug approval. Monsanto claimed no rats absorbed rBST in their blood stream–hence there was no need for long term toxicity studies–but Canadian scientists who obtained the study discovered that 20% to 30% of the rats did absorb rBST with biggest concentrations in (you guess it) the prostate. There were also thyroid cysts. 
This inspired Vermont Senators Patrick Leahy and James Jeffords to ask the U.S. Health and Human Services Department to formally investigate the FDA’s approval of rBST in 1998.  Especially since the FDA employee in charge of labeling guidelines for rBST, Michael R. Taylor, had been a Monsanto vice president. And the FDA researcher charged with evaluating rBST levels in milk had done the same work at Monsanto. 
And how about IGF-1, insulin-like growth factor-1, the rBST byproduct that’s associated with breast, prostate and colon cancer and may be in the milk? 
“IGF-1 is [a] naturally occurring human hormone commonly measured in our saliva,” writes Trent Loos, columnist for the Agribusiness weekly Feedstuffs on the rBST supporting web site <http://www.igf-1-and-milk.com/>www.igf-1-and-milk.com. “Every person who has ever been diagnosed with cancer has also had saliva. Does that mean that saliva causes cancer? NO. Furthermore, if parents are worried about the impact of milk consumption on their kids, are they keeping the kids locked away from the sun? Malignant melanoma [is] the most serious form of skin cancer.” Reassured? Me too.
Then there’s the mastitis.
Occurrences of mastitis–udder infections–and lameness are so increased under rBST, a Canadian Veterinary Medical Association panel’s report found, “Treated cows were at higher risk of being culled,” and rBST was banned. 
John Shumway, a Lowville, New York dairy farmer told an Albany newspaper he had to cull a quarter of his cows after using rBST for eight weeks. 
And “cull chronically-infected cows,” is actually one of the “general recommendations” Monsanto offers for mastitis management on its web site.
Not only does mastitis introduce antibiotic residues in milk and encourage antibiotic resistance, it has contributed to the wave of dairy downers seen in slaughterhouses in the last decade, food activists say. 
Some even claim the hopped up metabolic needs of rBST cows are what induced dairymen to feed downer cows to live ones in the macabre practice that transmitted mad cow disease.
As anti-rBST sentiment builds in the U.S. and the public says, “We’re drinking WHAT?” Monsanto executives contend that the new rBST-free milk offerings are a marketing ploy.
They know a little about marketing ploys.
MARTHA ROSENBERG is a Staff Cartoonist at the Evanston Roundtable. Her work has appeared in the Chicago Tribune, LA Times, San Francisco Chronicle, Boston Globe, Providence Journal. Arizona Republic, New Orleans Times-Picayune and other newspapers. She can be reached at: email@example.com
 Rutland Herald June 12, 2005
 AP Feb 19, 2005
 St. Louis Post-Dispatch Nov 6, 2006
 Captial Press Oct 20, 2006
 New York Times Oct 7, 2006
 Rutland Herald, Oct 7, 2006
 The Buffalo News March 9, 1994
 Capital Times Dec 18, 1998
 The Oregonian Feb 27, 2005
 New York Times Nov 9, 2005
 Wisconsin State Journal Aug 14, 1994