Aerial Herbicide Spraying- Poisoning the Maine (and New Hampshire) Woods
by Daisy Goodman
Aerial application of herbicides is a common forestry management tool in the United States and Canada, and one which is currently employed in the northern New Hampshire and Maine woods. In 1998, a total of 58,264 acres in Maine were sprayed with a mixture of herbicide products by nine companies, including Bowater, SAPPI, International Paper, Irving and Champion International.
Herbicides are used in forestry to eliminate primary successional species which grow following clearcutting. These plants, including raspberry, blackberry, pin cherry, aspen, yellow birch, and grasses, are considered pest species by the forest products industry, competing with the desirable secondary successional spruce and fir "crop" trees. Herbicides act by disrupting specific metabolic functions in plants, causing disorganized growth and eventually killing the plant through starvation. Because hardwood and brush species have a different seasonal life cycle than softwood species, herbicides applied in late summer and early fall kill deciduous species only.
Four herbicides are used in forestry applications in Maine: glyphosate, imazapyr, triclopyr, and sulfometuron methyl. All are classified as broad spectrum, meaning they kill a variety of plant species. However, most herbicide applications in Maine involve at least two herbicides, most commonly glyphosate and triclopyr. Imazapyr and sulfometuron methyl are added if there is a predominance of species resistant to the first two herbicides (for example, sulfometuron methyl is very effective against grass species). In addition to active ingredients, herbicide products contain a certain percentage of "inert" ingredients, whose identity is not released by the EPA, even through the Freedom of Information Act (FOIA) process, without the manufacturer's permission. Some inert ingredients are in themselves toxic, as in the case of GARLON 4, which combines a diesel fuel carrier with the herbicide triclopyr, and OUST, which includes a formaldehyde condensate with the herbicide sulfometuron methyl (see sidebar). Furthermore, the herbicide glyphosate requires the use of a surfactant to facilitate transport of the herbicide into the plant. Although the Maine Board of Pesticide Control does not require companies to report on surfactants used, glyphosate product labels specifically recommend use of the detergent-like surfactant POEA. This compound is a potent water contaminant known to be dangerous to aquatic organisms.
Unfortunately, almost all research on the toxicity and environmental fate of forestry herbicides is conducted on herbicide active ingredients in isolation. Sometimes herbicide products, including active and inert ingredients, are tested, but no research exists on the herbicide product combinations such as those in actual use in the Maine woods. Additionally, very little field research has examined the environmental impact of herbicide applications on the ecosystem level. The toxicology and environmental fate studies which are available, therefore, give only a partial, simplified image of the actual impact of forestry herbicides in a real forest ecosystem.
Aerial applications are typically made by helicopter from 60-80 feet above the target area. Because of the method of application and the chemical behavior of the mixtures used, movement of herbicides, surfactants and inert ingredients off target is both inevitable and extensive. According to researchers at EPA's Environmental Fate and Effects Division, off target drift is estimated by the agency at 45% of applied rate, and some percentage of spray may transport as much as two miles off site. Highly potent, mobile herbicides such as sulfometuron methyl and imazapyr require much lower concentrations to cause plant mortality, and therefor more widespread damage is likely to occur as a result of drift. Movement in soil (leaching) and surface water transport increase the area affected by herbicide applications. The herbicide sulfometuron methyl has been shown to be more mobile in water than the highly controversial water contaminant herbicide atrazine. Surfactants that are detergent like- such as POEA- are highly water soluble and wash off sprayed vegetation. Once dissolved in water, herbicide mixtures run off site and contaminating nearby bodies of water. Such off target movement greatly increases the area impacted by herbicide applications.
Herbicide applications alter the forest ecosystem on all trophic levels. On the microbial level, growth and function are dramatically diminished after herbicide applications. Both the essential bacteria which fix nitrogen in soil, and the micorrhizal fungi which facilitate nutrient uptake by a plant's root system are inhibited by most herbicides. Bacteria and fungi have similar metabolic functions to higher plants, and so are affected by herbicides in similar ways. The herbicide sulfometuron methyl, in fact, is recommended for use by the manufacturer as a soil sterilant, and the herbicide Triclopyr has been shown to suppress mycorrhizal fungal growth by close to 100% at a concentration of 1000 ppm.
After an herbicide application, the early successional plant species which prevent erosion and nutrient leaching from soil die. Loss of their stabilizing root structure leads to an increase in water movement through the soil, increased nutrient loss, and increased erosion from the spray site. In fact, soil nutrient loss from forest areas treated with herbicides has been shown to be greater than loss after either clearcutting or clearcutting followed by burning. The effect of herbicide treatments on soil quality and nutrient uptake by plants is compounded by the persistence of certain herbicides in soil. The half life of the herbicide imazapyr in soil is calculated as 49.5 months, and triclopyr was detected in soil at 365 days post spray.
Following herbicide treatment, regeneration occurs over the next several growing seasons for a reduced number of plant species. The herbicide triclopyr in particular has been shown to severely inhibit seed germination on the forest floor after forestry applications. Some species are able to grow more quickly in the presence of herbicide residues in the soil, these are typically the more vigorous primary successional species, including grasses and raspberry. More sensitive plant species may be eliminated altogether, strongly reducing forest diversity. Additionally, certain herbicides act to reduce a plant's ability to bear fruit at a sublethal dose level such as occurs with herbicide drift. Rare and endangered native plants are at great risk from interference with fruiting ability or seed germination.
Wildlife is adversely affected by forestry herbicide applications in many ways. First, the reduction of plant diversity limits availability of preferred foods, shelter, and breeding/rearing areas for young. During the first year after herbicide application, a very limited number of species regenerate, and wildlife population densities are drastically reduced. Avoidance of sprayed areas is reported for a number of years after herbicide treatment. As species that return to a given area seasonally are forced to re-locate, territorial boundaries are compromised and breeding and nesting behaviors are disturbed. Small mammals are more subject to predation due to loss of ground cover.
Wildlife is also directly affected by exposure to toxic chemicals. Although efforts are usually made to ensure that humans are not in target areas during spraying, other species are afforded no such protection. Exposure occurs through herbicide mixtures contacting fur and skin, through inhaled mist, and through eating sprayed foliage. Aquatic organisms are exposed to herbicides when water contamination occurs through drift or runoff from spray areas after rainfall.
Dermal (topical) exposure to herbicide products causes mild to severe effects, particularly to the eyes, depending on the active and inert ingredients. For example, imazapyr is classified by EPA as a "severe eye irritant", and the herbicide triclopyr requires a petroleum based carrier, typically diesel or kerosene, both of which are dangerous eye, skin and respiratory irritants. Exposure to diesel fuel reduces bird egg hatchability to almost zero.
Most herbicide products used in forestry have a severely irritating effect on lung tissue when inhaled. In particular, inhalation of kerosene or diesel causes potentially fatal chemical pneumonia. The combination of glyphosate and the POEA is linked to serious lung injury. This same combination causes inflammation of gill tissue in fish, especially in young fish, reducing survival. Even small amounts of diesel and kerosene in water are highly toxic to fish. The leaching of nitrogen from soil, increase in water temperature in sprayed areas also affects survival of cold water fish species.
Ingestion of herbicides can occur initially when an animal attempts to clean itself after dermal exposure- particularly likely if the substance is irritating, and chronically through eating plants containing herbicide residues. Although there is no visible damage to plants immediately after spraying (mortality may take up to six weeks), residues are present in plant tissue and herbivores may be exposed repeatedly while feeding within a spray area. Glyphosate residues have been found in animal tissues at six weeks following spraying, and triclopyr, because it is a fat-soluble compound, has been shown to accumulate in the tissue of mammals. Humans consuming animals exposed to triclopyr in particular should be concerned about herbicide residues in meat.
Herbicides are also associated with reproductive problems. A strong correlation has been made between glyphosate exposure and decrease in sperm count and increase in abnormal and dead sperm in mammals. Exposure to sulfometuron methyl is linked with atrophied and degenerated testicles in rats and dogs. Both studies cited above point to disruption of reproductive function on the endocrine level, the body's hormone regulatory system, and raise grave concerns about the long term impacts of exposure, particularly to combinations of pesticides and other toxic ingredients of pesticide products. To date, no studies are available which specifically address endocrine disruption by any of the herbicides currently in use in forestry in Maine.
Recently, pesticide exposure has been linked to immune disfunction in numerous studies. A study by Swedish oncologists Drs. Lennart Hardell and Mikael Eriksson published in the journal of the American Cancer Society in early 1999 has revealed clear links between glyphosate exposure and development of non-Hodgkins lymphoma, a form of cancer of the lymphatic system which has increased worldwide at an alarming rate in recent years.
The cumulative impact of aerial spraying on wildlife is poorly understood because of the narrow focus of the research available at this time. The combination of stressors which occurs through exposure to a mixture of herbicides, surfactants, and inert ingredients presents a far more serious threat to an individual's survival than is provided by a controlled study of one chemical and one exposure route in the laboratory setting. Claims by the forest products industry that aerial spraying is harmless or beneficial to wildlife are hardly supported by the limited scientific literature that exists, and there is a serious lack of research available. Existing evidence shows that this practice alters the forest ecosystem on all trophic levels, but the real environmental impact of extensive aerial herbicide applications in Maine and northern New Hampshire is unknown. Should we continue to allow a giant environmental experiment to continue without challenge?
And for the chemists among us...... product names/manufacturers/chemical
active ingredient: glyphosate
inert ingredients: water, FD&C blue No. 1
manufacturer: American Cyanamid
active ingredient: imazapyr
inert ingredients: glacial acetic acid, others- claimed confidential by manufacturer
GARLON 4 herbicide
active ingredient: triclopyr
inert ingredients: Dodecylbenzenesulfonic acid, Ethoxylated sorbitan monooleate, Petroleum solvent (usually diesel/kerosene)
manufacturer: EI DuPont
active ingredient: sulfometuron methyl
inert ingredients: sodium naphthalene sulfonate- formaldehyde condensate, sulfate of alkyl carboxylate, sulfate of alkyl naphthalene, polyvinyl pyrrolidone, trisodium phosphate, sucrose
manufacturer: EI DuPont
active ingredient: sulfometuron methyl
inert ingredients: sucrose, Sodium salt of naphthalene-sulfonic acid formaldehyde condensate, Polyvinyl pyrrolidone, Sodium salt of sulfated alkyl carboxylated and sulfate alkyl naphthalene, Hydroxypropyl methylcellulose
All information obtained through EPA via Freedom of Information