Jennifer Larsen

Environmental Geology Seminar

April 1999

Biradar, D.P. and A.Lane Rayburn. 1995. "Chromosomal Damage Induced by Herbicide Contamination at Concentrations Observed in Public Water Supplies." Journal of Environmental Quality, 24:1222-1225.

These researchers began with the hypothesis that chromosomal damage would probably occur on Chinese hamster ovary cells with their exposure to "safe" levels of three herbicides: atrazine, simazine, and bentazon. Of the three herbicides, chromosomal damage consistently occurred when the ovary cells were exposed to atrazine concentration levels currently accepted as "safe" for the public drinking water supply. This study only considered an exposure of 48 hours of the cells to the contaminants. The possible repercussions, therefore, of an individual’s exposure over time are sobering. Especially with consideration for children and their water consumption, it is imperative that further study continues in this effort and that the public supports serious legislation to protect our drinking water.

Plain and simple I liked this article. I especially appreciated that the researchers were willing to assess the possible damages of chromosomes at the herbicide contamination level considered safe by the government and consequently by the public. This seemed to me to be a much more applicable approach and a strong case for cleaning up our public drinking water supply. This should be a demand from the public at large and it should be a priority by those whom we elect to govern.

Davis, Devra Lee and H. Leon Bradlow. 1995. "Can Environmental Estrogens Cause Breast Cancer ?" Scientific American, October 1995:166-172.

The authors have collaborated in an attempt to identify causes for breast cancer in women who show no signs of known risk factors. Two out of three women with breast cancer are in this category. Davis and Bradlow have produced a substantial amount of data that suggest that xenoestrogens might be accountable for these cases of questionable origin. Xenoestrogens are foreign sources that can either alter the normal hormone activity or mimic the normal activity. There are many known sources of xenoestrogens including plastics, fuels, drugs and pesticides. Among the commonly identified sources of xenoestrogens is atrazine, the most commonly used herbicide in the United States today. These researchers proclaim eliminating the presence of these xenoestrogens from everyday human contact could minimize the number of breast cancer cases caused by xenoestrogens.

The presentation of the material in this article was very readable and very convincing. The authors referenced many other recent studies, some which refuted their stance and most which substantiated their position. However, they readily admit in the third paragraph that much of their argument is purely speculative. Clearly the merits of this claim need to be further investigated.

Hanson, J.E., D.E. Stoltenberg, B. Lowery, and L.K. Binning. 1997. "Influence of Application Rate on Atrazine Fate in a Silt Loam Soil". Journal of Environmental Quality. 26:829-835.

This study was undertaken to investigate the mobility of atrazine in a prime agricultural soil in Wisconsin, and to find out under what application rates atrazine would be consequently found in the groundwater. Atrazine is readily dissolved in soil water and is therefore highly mobile in the soil/groundwater system. Also, it degrades to several byproducts easily, including deethylatrazine and deisopropylatrazine. These two byproducts maintain the mobile characteristics and therefore are used as an additional measure of atrazine presence in groundwater. The authors’ findings concluded that with increasing rates of atrazine application, more atrazine was found in the drainage water samples. At lower rates of application, it seems that the soil can hold on to a greater relative proportion of the atrazine, allowing less atrazine to enter immediately into the drainage water.

The figures used in this paper were very clear and very appropriate to their findings. I appreciated the motivation of these scientists for choosing this research topic and the applicability of their findings. Another simple example when more is not better.

Lakshminarayan, P.G., Aziz Bouzaher, and Jason Shogren. 1995. "Atrazine and Water Quality." Journal of Environmental Management. 48:111-126.

This paper outlines an economic and environmental model to assess 5 different programs of atrazine use and their cost-benefit tradeoffs. The model considered a "complete atrazine ban, a complete triazine ban, an atrazine restriction that allows post-emergent applications, and an atrazine ban based on either the maximum contaminant level (MCL) at 3 ppb or the 10-day Health Advisory Level (HAL) of 100 ppb". With no appreciable gains in water quality, and at a cost of 240 million dollars the model suggests a complete ban on the use of atrazine would be totally infeasible. Another conclusion of this model is that the cost per unit of corn would rise too much. There was no mention of time in the equations, or how long these costs would be so great. Their conclusions also state that They believe an atrazine restriction should be based on the maximum contaminant level (MCL) of 3 ppb or the 10-day health alert level (HAL) of 10 ppb. They assert further however that with enforcement and monitoring these regulations would still cost $160-230 million.

The "costs" as intimated by the authors, were those incurred mostly by the chemically dependent farmers being forced to switch to herbicides that simply cost more. Those higher costs would of course, immediately transfer to the marketplace. It was an obvious slant with the authors that there was no consideration whatsoever that a complete ban on atrazine would be of a great health benefit. The short term costs would be outweighed by the great gains in the long term quality of the public drinking water supply and the long term health of the public at large. Basically, this seemed to be a cold, economic based analysis that was incapable of accepting the input of the dollar value on human health. I did find it a worthwhile read, however. They did include in their model an "exposure value" that seems to address the human component. I had some trouble with a few of their assertions and more concretely, their tables, as they did not present the data with respect to a unit of time.

Levanon,D., E.E.Codling, J.J.Meisinger, and J.L.Starr. 1993. " Mobility of Agrochemicals through Soil from Two Tillage Systems". Journal of Environmental Quality. 22:155-161.

This study assessed the movement of five commonly and prolifically used agricultural chemicals through soils and compared two different tillage methods; plow-tillage and no-tillage. The five chemicals were atrazine, metolachlor, diazinon, carbofuran, and ammonium nitrate. To no great surprise, the no-tillage soil needed fewer amendments and was a much healthier and sustaining environment in which to grow crops. The disturbed and undisturbed soil both underwent three different leaching events, and the leachate was collected and analyzed. There were three groups of analytes assessed. They were bromide, nitrate-nitrogen, and the pesticides.

The results clearly showed that there was a greater flow of the pesticides through the plowed soils versus the non-till soils. The authors emphasize the inappropriateness of applying these results directly to real-life situations, as there are certain conditions that are not reproducible in a laboratory setting.

It was concluded that because the no-till soil maintains a higher organic matter and a lower pH and therefore, has a greater microbial population, it allows for more sorption of the pesticides. The higher microbial population would allow for greater degradation of the pesticides as well, reducing the total amount of pesticide available for leaching into the groundwater.

I liked the approach of these researchers, but I felt that there were some glaring omissions in the set-up of their research methods. In their methods section, they described the incubation and leaching process where 8 liters of water were applied to the soil cores and the leachate was collected. They collected until the "column drainage became very slow". This phrase leaves too much for the next researcher to guess. Perhaps they could have defined it to a point of less than 10 drops per minute or some other measureable volume. As well, I also think they should have more clearly expressed their definition of the phrase "disturbed surface soil". It was unclear if they considered a disturbed soil to be a soil that had been plowed for the last twenty years on a yearly basis, or if it had been disturbed in the past month.

I believe the premise of their research is very important. When using these chemicals it is critical to consider their long-term environmental consequences along with the value of their original use. This study looked at the possibility that different field practices could create different sets of consequences with regard to the amount of pesticides that make their way directly to the groundwater.

Pereira, Wilfred E., and Frances D. Hostettler. 1993. "Nonpoint Source Contamination of the Mississippi and its Tributaries by Herbicides". Environmental Science and Technology. 27:1542-1552.

Because the Mississippi River is such an important source of public water supplies, the realization that the river, and its tributaries, were contaminated was a serious motivation for these scientists. The Mississippi River travels through fourteen states and one of the United States’ major agricultural regions. Due to the significant amount of territory covered by the tributaries of the Mississippi River, it is highly influenced by nonpoint source pollution. Although the research for this particular study was begun in 1991, this study is a continuation of research on pesticide transport on the lower Mississippi that occurred during 1987-1989.

Atrazine was identified as the pesticide most prolifically used in the fourteen-state region. Although pesticides are typically applied only during the growing season, this study found that pesticides were present year round in the Mississippi River system. The authors concluded that the pesticides collected in areas such as alluvial aquifers during the spring and summer months. During the lower flow months of the winter, these pesticides would once again enter the river system through the groundwater.

The staggering data present that in 1991, even with a low estimation of annual mass transport, 160 tons of atrazine were discharged into the Gulf of Mexico. It is clear that not enough is known on this topic. It would be interesting to see smaller versions of this study focus on the tributaries, and thereby, piece together a more accurate picture of the serious nonpoint source pollution problem of the Mississippi River system.

This study was vast in its scope and sobering in its conclusions. The researchers did not shy away from the serious point that even with "responsible" use, these agrochemicals have a great and far-reaching effect. The fact that so many of these chemicals and their degradation products eventually show up in a river system used as a public drinking water supply for millions of people, is overwhelming.

Spalding, Roy F., Daniel D. Snow, David A. Cassada, and Mark E. Burbach. 1994. "Study of Pesticide Occurrence in Two Closely Spaced Lakes in Northeastern Nebraska." Journal of Environmental Quality. 23:571-578.

In this study, two man made lakes, Maskenthine Lake and Willow Lake, were monitored for pesticides. Lake water samples, sediment cores and runoff samples were analyzed for pesticide concentration. Maskenthine Lake, created in 1975-76, is fed only by rainfall. Willow Lake, created in 1982, is fed by a continuous stream from Willow Creek.

The researchers used the Agricultural Nonpoint Source model (AGNPS) to assess the differences in runoff, sediment and nutrient transport from the two watersheds. The model used for this study considers pesticide inputs to the watershed to originate from runoff and sediment erosion. The highest pesticide peaks were noted during the rainy spring months of May and June. This coincides with the large applications of pre-emergent pesticides that are associated with the spring planting regime.

The results showed a frequency of 100% of atrazine in each lake water sample for Maskenthine Lake and 98% for the Willow Lake samples. The study found 10 pesticides present in both lake systems: alachlor, atrazine, cyanazine, EPTC, fonofos, metolachlor, propachlor, mertribuzin, simazine, and trifluralin. Of these pesticides only cyanazine, atrazine, fonofos and two byproducts of atrazine breakdown, deethylatrazine (DEA), and deisopropylatrazine (DIA), were found to be at levels greater than 1ug/L.

Maskenthine Lake was considered the more vulnerable system because of its dependence on runoff inputs. Throughout the study, atrazine was consistently monitored at >3 ug/L after the initial spring flush. Atrazine was found to be generally associated with the top centimeters of the lake sediment samples. While the root-worm pesticide, fonofos, was found to be present all through the core sediments.

I was curious as to why these researchers called on the AGNPS model to further substantiate some of their research findings. Perhaps this shows my inexperience with models, but on many occasions they had to make up several parts to the input equation to account for the real-life situation. Beyond that, their sampling scheme appeared to be very thorough and their discussion incorporated the conclusions of many other similar studies, which again well substantiated their findings.