I read with interest the letter "Spartina herbicide has been extensively studied, works well" by Miranda Wecker. I have done research on herbicide mixtures' subtle low-level effects for more than 25 years. I should also point out that I work with the commercial formulations, not just the "reagent grade" active ingredients.
Most people do not realize that 1) what is registered as a pesticide is not what is sold to the consumer. The nonionic solvents and surfactants added to improve the lipid and water solubility of an "active" ingredient are never tested in the context of the formulations. The few studies that have explored this find changes in activity with the addition of these solvents and surfactants.
Most people do not realize that 2) there are at least six major shortcomings to the registration process of every pesticide formulation. They are documented in a paper we published in 1999 which summarizes five years of research on two of the most common pesticides used: atrazine and aldicarb. This paper is in two parts on my home web page, which is: www.zoology.wisc.edu/faculty/Por/Por.html That work also studied the impact of the presence of nitrate in the water as well. (Why is nitrate important? Because it interacts with a subgroup of key defensive enzymes of the body to "disable" them, thereby making the organism more vulnerable to attack by foreign molecules.) All concentrations were environmentally relevant and at levels that EPA considered "safe." We showed through a series of 12 successive experiments that these mixtures were capable of altering aggression levels, altering immune function, and altering hormone levels. There are no collective neurological, immune and endocrine tests that the EPA does for any chemical as far as I am aware.
Most people do not realize that 3) our hormonal and immune systems operate in response to chemicals in the parts per trillion and low parts per billion and that the EPA has no tests at those concentration levels. In fact most instrumentation for measuring these chemicals cannot get that low.
Most people do not realize that 4) fetuses respond at the same levels as adults to chemicals in their body, but they have none of the detoxification mechanisms that sexually mature organisms have. Thus, they have their "hands tied behind their backs" in terms of ability to respond to toxic chemicals.
Most people do not realize that 5) pesticides are designed to be both lipid and water-soluble. The lipid solubility is typically the ring shaped structure present in a pesticide active ingredient. The water solubility part is represented by various groups attached to this ring that may be acid groups or various ions, such as chloride ions. These solvents and surfactants added to the mixtures are intended to enhance these two solubility properties. Why is this important? Lipid solubility allows a molecule to penetrate waxy surfaces, like the skin or the waxy surface of a leaf, which is a primary barrier against foreign chemicals. Lipid solubility is also the universal master entry key for every cell in the body of an organism. Once inside a cell a pesticide molecule's water solubility becomes particularly important. Water solubility means that there are strong electrostatic charges attached to the molecules of pesticides, which may cause them to interact with any oppositely charged molecule inside a cell once entry is gained. This may include among other things DNA, mitochondria, a variety of proteins and other molecules that may be promoters or inhibitors of genetic expression, various ions in the cell, such as sodium, potassium and chloride, which can function as intra- and intercellular communication mechanisms. Thus, the possibilities for subtle biological impacts are broad, enormous, and unpredictable and in some cases may not show themselves for years after exposure.
Pesticide formulations "work well" because they can pe
netrate the skin and respiratory services of organisms, bypassing body defenses if they exist, and cross the surfaces of reproductive organs and the cells that compose them as well as any other type of cell in the body and interact with molecules carrying on life processes. There are numerous studies in the literature documenting subtle impacts on learning abilities, immune function, hormonal changes, and developmental problems. There is clear evidence that humans and especially fetuses and children can be impacted in serious ways that affect the rest of their lives. There have been recent studies demonstrating that pesticides are capable of exerting genetic effects or epigenetic effects over multiple successive generations. This is of grave concern.
Most people do not realize 6) that recommended pesticide mixtures that include multiple active ingredients are virtually never tested for these mixtures effects, yet studies in the literature demonstrate that frequently these mixtures have added effects that were unanticipated and sometimes nonlinear. It is my understanding that pesticide mixtures, not a single chemical, have been used to attack Spartina.
Most people do not realize 7) that industry representatives now sit on EPA panels that make important decisions regarding pesticide regulation. These people clearly have potential for conflict of interest, yet under current practice they are allowed to participate and potentially alter panel functions/decisions. This also has been documented by several authors.
Most people do not understand that everything is interconnected. They also seem to forget the fact that there are always non-toxic alternatives. Vinegar is extremely effective in killing plants for example. There are excellent sources of information on alternative control measures if necessary for modulating the abundance of organisms. One such example is the excellent IPM source http://www.stephentvedten.com/
One question that nobody seems to have asked in this particular controversy is why and how did a grass that for years was limited in its distribution suddenly explode across such a large area? Did the natural defenses of the bay finally get overwhelmed which allowed this plant to expand so rapidly?
Dr. Warren Porter