map of most dioxin-sprayed areas of Vietnam

Provinces	Population in 2009 (millions)	Percentage of Province Sprayed During 1960s	Gallons of Herbicides Sprayed	Total Area Sprayed (sq. kms.)	Rank Among Most Heavily Sprayed Provinces in Vietnam
Da Nang Cluster
Thừa Thiên Huế	1.1	25%	920,497	1,244	3rd
Quảng Nam/Đà Nẵng	2.4	8%	665,431	899	7th
Quảng Trị	0.6	17%	613,062	828	9th
	4.1		2,198,990
Phu Cat Cluster
Kon Tum	0.4	11%	818,340	1,106	4th
Binh Dinh	1.5	10%	450,817	609	10th
	1.9		1,269,157
Bien Hoa Cluster
Đồng Nai	2.6	41%	1,785,897	2,413	1st
Bình Phước/Bình Dương	2.5	24%	1,714,609	2,317	2nd
Tây Ninh	1.1	23%	690,160	933	5th
	6.2		4,190,666

Today these ten provinces are home to over 12 million Vietnamese. 

https://www.aspeninstitute.org/programs/agent-orange-in-vietnam-program/maps-of-heavily-sprayed-areas-and-dioxin-hot-spots/

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In 1988, Dr. James Clary, an Air Force researcher associated with Operation Ranch Hand, wrote to Senator Tom Daschle, “When we initiated the (largely covert) herbicide program in the 1960s, we were aware of the potential for damage due to dioxin contamination in the herbicide.  However, because the material was to be used on the enemy, none of us were overly concerned.”    https://www.history.com/topics/vietnam-war/agent-orange    

  Dow, Monsanto and other companies produced this poison.  After Vietnam War the US National Forest Service used it in Washington, Oregon and at Mt. Shasta for various reasons.  It was a long fight. -r