"GREAT PLUMES OF BROWN FUMES blossomed above concrete canyons, climbed thousands of feet into the air and drifted sideways as they cooled, blown by the winds aloft...The plumes cooled and descended on the desert where iodine vapor struck to the Artemisia leaves: these leaves were eaten by the rabbits, which in turn were eaten by the coyotes..."
—Michelle Stenehjem Gerber, On the Home Front
Airborne releases of radioactive materials were the result of routine operations and occasional accidents but others were planned and intentional. The most notorious intentional release of its kind occurred in 1949. Code named the Green Run, this classified experiment deliberately released 8,000 curies of radioiodine during a single event occurring over two days. A total of 166 documented radionuclides were released into the atmosphere from the Hanford facility during its active production lifespan.
Additional routine operations produced radioactive materials that were dispersed into the air after plutonium, previously removed from the reactors, was separated and purified for use in nuclear weaponry. In 1945 alone, it is documented that 345,000 curies of iodine-131 were released into the atmosphere.  In comparison, the March 1979 Three Mile Island accident released between 15 and 24 curies of radioactive iodine. Winds carried airborne radiation throughout eastern Washington and northeastern Oregon continuing eastward into northern Idaho, Montana, and Canada. It is estimated that between 1944 to 1957 over 740,000 curies of radioiodine were released into the atmosphere above the Pacific Northwest.
Iodine-131 (radioinodine) is one of the more dangerous fission byproducts that negatively affects both human and animal health. It is a beta-emitter with a half-life of approximately eight days. Radioiodine has the same ability to concentrate in the thyroid gland as non-radioactive iodine. An individual exposed to iodine-131 can suffer acute and chronic health effects, including thyroid cancer, benign thyroid growths, and overall inhibited thyroid performance.
Early on Hanford officials were well aware of the potential dangers of iodine-131 but did nothing in the way to alert their workers or the surrounding communities. Classified studies done at Hanford revealed how radioiodine traveled through the food chain, increasing in concentration as it moved upwards into higher consumer species. Clandestine studies conducted at Hanford revealed how high dosage levels of ingested iodine-131 in sheep showed "virtually complete destruction" of their thyroids and those of their offspring.  Hanford officials repeatedly assured the public that, "not one atom" has escaped the facility. At one press conference officials stated bluntly that the facility was "safe as mother's milk" even as they were well aware of the possibility of compromising the health of both workers and the general public through Hanford's plutonium production activities. 
Iodine-131 was invisibly transferred from Hanford facility to area residents through the consumption of locally grown produce harvested from contaminated sites or through milk taken from cows who had grazed on contaminated forage. Many rural residents in the surrounding areas drank milk from their own herd or from local dairies. Many residents consumed fruit and vegetables grown from backyard gardens or local family farms. Others, including local Indians, practiced subsistence hunting and fishing in areas in and around the Hanford facility and were consequently dosed with radiation when contaminated animal flesh was consumed.
In general, children are more susceptible to the harmful effects of radioactive exposure than adults. As the largest consumers of milk, local children were exposed to iodine-131 through consumption of contaminated cow's milk or worse, from their mother's own breast milk. Studies show that a female exposed to radioactive material will, in turn, secrete harmful radionuclides into her milk and pass it to her nursing offspring in a more concentrated form.
During the mid-1940s, the Richland Village milk supply was brought in from Ellensburg and Yakima as acreage for grazing within town limits was unavailable for pasture. A secret milk-testing program was initiated in 1945 to discern "gross beta" radiation estimates as no technology existed to test milk specifically for iodine-131. Hanford health officials never publicly disclosed to Richland village residents that they were indeed checking the milk for radioactive contamination. Officials instead stated that they were testing milk for "bacterial count and butterfat content" among other seemingly inconsequential reasons—the true nature of these tests were never revealed. 
Hanford officials had additional undisclosed concerns regarding iodine-131 which is evident in early public education "safety campaigns." One such campaign developed in 1945 promoted the consumption of iodized salt to possibly "reduce the uptake of the latter [iodine-131] by the thyroid" of Hanford workers and area residents by having Hanford workers guess how many salt tablets were contained in a jar at the workplace.  Not so soon after the campaign appeared the Richland community newspaper announced, "Medical Department Recommends the Use of Iodized Salt." General Electric physicians went on to say that because "inland regions with little rainfall [such as the Columbia Basin] tend to have lower iodine content in the water and soil...The body needs a certain amount of iodine...we recommend that you use iodized salt." 
Iodine-131 is considered the largest "dose" component of the 166 documented radionuclides released into the atmosphere at Hanford. "Dose" refers to the amount of radioactive energy absorbed by body tissues. According to the Hanford Environmental Dose Reconstruction Project (HEDR) other longer-lived radioisotopes contributing to dose were cerium-144, plutonium-239, ruthenium-103, ruthenium-106, and strontium-90. Possible health problems associated with dose exposure include a variety of cancers including leukemia as well as reproductive dysfunction and chromosomal aberrations.
Unlike the atmospheric releases of iodine-131 another dangerous situation arose when cerium, plutonium, and strontium particulate matter became attached to rust or dust specs during the uranium irradiation process. These radioactive particles, referred to as "hot particles" were discharged into the atmosphere during the separations process. Eventually the microscopic particles made their way into the processing plants' ventilation system. Over time the interior of the ventilation system began to rust and corrode shedding contaminated matter into the stacks. Due to the size and weight of the particles many landed within the Hanford site boundaries but others were detected as far as east as Mullan Pass (now known as Lookout Pass) in Idaho and as far west as Mt. Ranier.  The largest of these releases took place from 1944 to 1954. Although Hanford officials required filtration masks for facility workers the majority of the construction workers and security staff were not issued any type of respiratory protection. 
After World War II a new type of chemical process was developed to recover plutonium from irradiated fuel. Unintentionally this "reduction-oxidation" process known as "Redox" for short, created a flaky byproduct that included radioruthenium. In 1952, shortly after Redox plant operations had begun, technicians discovered ruthenium particles occasionally "large enough to be seen by the unaided eye" with snowflake-like radioruthenium particles occasionally observed several inches in diameter.  The largest reported release of radioruthenium was in January 1954 when nearly 200 curies were released from the Redox plant. Technicians observed these radioruthenium particles 150 miles northeast in Spokane and later discovered traces of the same airborne particles in northeastern Montana in 1954.