The use of some toxic pesticides may be warranted.

Not all pesticides are created equal and some, as we all know, are more toxic than others. The EPA has been reviewing the data on many of the older pesticide categories for some time now and using new guidelines to determine if their uses are still safe.

One active ingredient that is going through this process is Chlorpyrifos. Because of its high mammalian toxicity it is getting a good review. The EPA has made some changes to how this product is being used with its first ruling back in 2000 eliminating all residential uses except for roach bait in protective bait stations. Then back in 2002 it banned the use of the product on tomatoes and made some further restrictions on its use on citrus, tree nuts and other crops. In 2012 the EPA limited the use of chlorpyrifos by lowering application rates and creating no-spray buffer zone requirements.

“Chlorpyrifos can cause cholinesterase inhibition in humans at high enough doses; that is, it can overstimulate the nervous system causing nausea, dizziness, confusion, and at very high exposures (e.g., accidents or major spills), respiratory paralysis and death.”1 Most of the issues with this product has been occupational exposures that applicators would experience and most of those concerns have been addressed through training and strict personal protective equipment requirements.

Why does keeping the use of this product matter for agriculture? Chlorpyrifos is used in corn and soybeans and, because of the large number of acres of these crops, these uses are the largest for this product. Many of these applications are seed treatments, but it is also used on fruits and nut trees, and a limited number of vegetable and row crops as well. Uses have already been restricted as a result of the EPA’s re-registration process. For example, on fruit trees and grapes, it can only be used during the dormant season and on citrus and vegetable crops the harvest intervals have been greatly increased. Most of the foliar application on crops are done because there are pests that are very difficult to control and this product happens to be one of a few that will work. Aphids on asparagus, broccoli, cabbage, and soybeans, as well as leaffooted plant bugs on almonds, are the most common needs for a foliar application I come across. Even though there are other products that can work to control these pests, the lack of products to rotate with means the loss of chlopyrifos runs the risk of developing resistance to those few products faster. “Matthew E. O’Neal, Iowa State University entomologist said when it comes to soybeans there should be some concern about what a chlopyrifos ban could mean in years to come. ‘My concern is if we get into a situation where we have a resistance to the other classes of insecticides used for aphids we’re going to need an alternative,’ he said. ‘Chlorpyrifos is commonly used by farmers for aphids and other pests in soybeans. If one class of insecticide replaces its uses in soybeans, this could increase the likelihood of resistance occurring. In four or five years that’s when you’d start to notice there are is no chlopyrifos and you’re looking for something that works.'”2 This warning holds true for the other critical uses as well. Without the use of chlopyrifos in asparagus for aphids those growers will have a hard time getting a crop to market as many other aphid control products are no longer effective on asparagus aphids.

Knowing that the EPA was reviewing the uses of chlopyrifos and that some concerns (which I will address later) had been brought up, University of California, California Department of Pesticide Regulation and industry stakeholders made a thorough assessment of the critical uses of chlopyrifos in some key crops grown in California and have made some recommendations on how to successfully manage the use of this product. The 198 page document reviews the key uses of chlorpyrifos in four key crops in the state. “The four crops represent $10 billion in annual revenue and cover 2.4 million acres of cropland. During the period of 2002-2012, 61% of the total chlorpyrifos use was recorded on these four crops.”3 The study pointed to an overall decrease in the use of chlorpyrifos with some years showing a slight increase, no doubt due to spikes in pest pressure. These spikes in the amount of product used has caused concern in some areas due to the human and environmental risks associated with chlorpyrifos. Note: since the CDPR report came out a new product to control aphids in alfalfa has been registered and the situation for that crop and chlorpyrifos use has improved.

The major cause for concern now is the previously identified drinking water issues and dealing with a petition from the Natural Resources Defense Council (NRDC) and Pesticide Action Network North America (PANNA). This is the petition the court has addressed in determining that the EPA timeline for evaluating the drinking water issue was not adequate. The EPA’s 2014 revised human health risk assessment confirmed a potential risk to drinking water in small watersheds near areas where chlorpyrifos is widely used. These small watersheds are generally less than 40 square miles and in small regions of the country. The examples are outlined in the revised risk assessment. 4 “The 2014 assessment included a refined drinking water assessment for the Pacific Northwest and the Southeast, but not the entire country. The EPA has determined that safe levels of chlorpyrifos may be exceeded for people whose drinking water is derived from certain vulnerable watersheds in parts of the United States.  the EPA is continuing to work on its refined regional drinking water assessment in order to identify those vulnerable watersheds.”5

Can the drinking water issues be addressed without banning all the uses for chlorpyrifos? Since the problem seems to be isolated to small watersheds near well-defined areas of high chlopyrifos use, it seems that other ways to mitigate the problems should be examined. The work published in the CDPR “Chlorpyrifos Critical Use” report shows that a well thought out approach to this problem is achievable. The report outlines uses to focus on and best use practices to hopefully reduce levels of chlopyrifos in surface water that are exceeding tolerances. Research and education are key components of the process. Farmers and those making pest control decisions need to be aware of the potential problems surrounding the use of chlorpyrifos and need to be willing to make decisions that will help keep the product out of local waterways. But in order for such an approach to work, all stakeholders involved must be on board and willing to follow best use practices.

California’s State Water Resources Control Board has surface water monitoring programs in place and have been monitoring water for a number of contaminants including, but not limited to, certain pesticides, such as chlorpyrifos. Their Irrigated Lands Regulatory Program has many years of data showing where contaminants have been found and at what levels. Data since 2006 has shown some improvements in surface water chlorpyrifos contamination but some areas are still showing exceedances, and some of those areas were not involved in the crops mentions in the DPR critical use program. More investigation and outreach seems to be needed.

So what does all this mean for the fate of chlorpyrifos? Unfortunately the regulatory process does not have a good track record for making policy based solely on scientific evidence, and there are many public groups that have very little patience with any attempt to develop programs that will keep pesticides they are not happy with in use. Research, data collection, programs, and outreach all take time and money. Budgets are tight ,and the number of people with expertise in these areas are declining, making resources available to work on these issues very tight. Public distrust of government regulators is on the rise at the same time government continues to cut budgets for the science needed to address these issues. EPA is forced to rely more and more on industry supplied data which increases the public distrust of the current system. The current public comment period for the proposal to revoke the tolerances for chlopyrifos will be over by the end of the year. Stakeholder groups on both sides of the issue are currently sending in their views on the matter. It would be nice to see a measured and thought out approach to making sure this product can still be used where it is needed come out of this process.

Footnotes
1. http://www2.epa.gov/ingredients-used-pesticide-products/chlorpyrifos
2. You’ll Still Have Pesticide Options If Lorsban’s AI is Banned – DTN
3. CDPR Critical Use Report
4. EPA’s revised human health risk assement for chlopyrifos
5. Proposal to Revoke Chlorpyrifos Food Residue Tolerances

 

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