I have ALWAYS been a strong believer in the relationship between PD and environment toxin...which, in the modern world, are in every breath we take, every bit of food we take, etc.

Ron, this information speaks directly to the fact that PD is different in each and every PWP. To the fact that we all progress differently and our brains are effected differently. This includes our sypmtoms and our cognitive issues.

This bolded quote is interesting also, and suggests that as our world become more toxic...goodness, think of the future.

"Scientists continue to study environmental toxins such as pesticides and herbicides that can cause PD symptoms in animals. They have found that exposing rodents to the pesticide rotenone and several other agricultural chemicals can cause cellular and behavioral changes that mimic those seen in PD. Other studies have suggested that prenatal exposure to certain toxins can increase susceptibility to PD in adulthood. An NIH-sponsored program called the Collaborative Centers for Parkinson's Disease Environmental Research (CCPDER) focuses on how occupational exposure to toxins and use of caffeine and other substances may affect the risk of PD."
Source: http://tinyurl.com/jfexb

There is other research regarding the BBB:
"The other project will use PET imaging to compare the blood brain barrier of people with Parkinson's disease to those who do not have the disease. It is hypothesized that biochemical changes that occur in the blood brain barrier of people with Parkinson's could allow greater accumulation of environmental toxins in the brain. If researchers are able to quantify these changes they may be able to identify people with the disease early and to track disease progression, as well as enable the targeted development of therapies that may restore normal blood brain barrier function."
Source: http://www.michaeljfox.org/research/grants.php?id=22