Dr Subra explained that exposure has been prolonged enough to create long-term effects, such as "liver damage, kidney damage, and damage to the nervous system. So the presence of these chemicals in the blood indicates exposure."
Testing by Dr Subra has also revealed BP's chemicals are present "in coastal soil sediment, wetlands, and in crab, oyster and mussel tissues."
Pathways of exposure to the dispersants are inhalation, ingestion, and skin- and eye-contact. According to Dr Riki Ott, symptoms of exposure include headaches, vomiting, diarrhea, abdominal pains, chest pains, respiratory system damage, skin sensitization, hypertension, central nervous system depression, neuro-toxic effects, genetic mutations, cardiac arrhythmia, and cardiovascular damage. The chemicals can also cause birth defects, mutations and cancer.
Dr Ott, a toxicologist, marine biologist, and Exxon Valdez survivor, told Al Jazeera that these chemicals "evaporate in air and are easily inhaled, they penetrate skin easily, and they cross the placenta into fetuses. For example, 2-butoxyethanol [a chemical used in oil dispersant Corexit] is a human health hazard substance; it is a fetal toxin and it breaks down blood cells, causing blood and kidney disorders."
To see the slideshow, go here.
"Solvents dissolve oil, grease, and rubber," Ott continued. "Spill responders have told me that the hard rubber impellers in their engines and the soft rubber bushings on their outboard motor pumps are falling apart and need frequent replacement. Given this evidence, it should be no surprise that solvents are also notoriously toxic to people, something the medical community has long known."
In March 2011, the US National Institutes of Health (NIH) launched a long-term health study of workers who helped clean up after BP's oil disaster.
Some scientists and toxicologists believe oil clean-up workers should have worn respirators and full protective clothing [Erica Blumenfeld/Al Jazeera]
According to the NIH, 55,000 clean-up workers and volunteers in Louisiana, Mississippi, Alabama and Florida will be checked for health problems, and participants will be followed for up to 10 years.
The study is largely funded by the NIH, which received a "gift" from BP to help run the study. BP says it is not involved in the study, which will cost $34m over the next five years.
But the study focuses mainly on people who participated in the clean-up, and does not include coastal residents such as Lorrie Williams and her family.
Al Jazeera asked Louisiana Governor Bobby Jindal what his state was doing to safeguard people against chemical poisoning.
In a statement to Al Jazeera, Jindal's office said:
"Coastal residents and response workers will be compensated through the deal reached between the Plaintiff Steering Committee and BP. BP must follow through on making whole [properly compensating] impacted residents and workers who experienced or are still experiencing health impacts as a result of the spill."
Stuart Smith, a New Orleans lawyer representing more than 1,000 cases against BP, most of them health related, has stronger words about the situation.