Pesticides in Water

Pesticides in Water

It used to be thought that groundwater was relatively pristine. This is no longer the case as pesticides leach into groundwater and runoff into rivers, lakes and reservoirs. The actual picture is not yet clear. Many laboratories are not equipped to measure the presence of pesticides in water and those that are are limited in the number they test for.

Question #1: What are pesticides in water?

Pesticides represent a large group of chemicals that are used to control plants and insects. For example, there are pesticides used to kill weeds, others used to kill mosquitoes, others used on farms to kill the pests that would destroy that particular crop.

Pesticides are used widely on farms, in orchards, on golf courses, on land used for railroads or high tension lines, and on lawns and gardens in residential areas. They are used for termite control and bug control. They are by their very nature toxic and designed to kill specific plants or insects.

There are different types of pesticides:

• Herbicides are used to kill weeds.
• Insecticides are used to kill insects.
• Nematocides are used to destroy certain types of worms.
• Fungicides are used to control molds, mildews and rusts.

Pesticides are a subcategory of what is called synthetic organic compounds. There are more than 700 synthetic organic compounds and pesticides is just one kind of these synthetic compounds.

Question #2: How do pesticides get into our drinking water?

Pesticides get into our drinking water through a number of routes. Surface water runoff will carry pesticides from farms, orchards, golf courses and residential properties into lakes, rivers and reservoirs. Other rain and snow water will seep into the ground and go into ground water taking with it some pesticides which then turn up in well water. Then too, there are improperly disposed pesticides and improperly applied termite pesticides that end up seeping into our drinking water supplies.

There are many factors that influence how much pollution takes place. Some pesticides dissolve quickly and enter our water supplies quickly. Others dissolve slowly or hardly at all and take much longer to get into the water supply if at all. The nature of the ground also affects the ease with which pesticides get into water supplies. Sandy soil permits pesticides in water to pass more easily. The depth of the ground water also affects how quickly pesticides get into it.

For example, one of the places where pesticides in water have shown up in well water the most is on Long Island. Not only is the ground sandy, but the water table is shallow and a lot of the land is used for farming. All factors conducive to leaching pesticides into ground water.

Question #3: How can pesticides in water affect my health?

Current knowledge of the effects of pesticides in water on health is still very much in the process of evolving. Tests are performed on laboratory animals and then estimated for humans. Long-term effects are hard to determine because they are accumulated over a lifetime of exposure.

Health effects depend on the kind of pesticide one is exposed to and the amount or concentration one is exposed to. Other components in the mix are how long has the exposure been and what is the overall health of the person exposed. All these effect the outcome.

In general, however, acute or high levels of exposure to pesticides in water may include such things as headaches, dizziness, stomach and intestinal upset, numbness, spasms, convulsions and heart attacks. Again, in general, long term exposure and its effects are not completely understood. Some pesticides are suspected of causing cancer long-term. Then, we know even less about is the effect of how one compound might interact in combination with others in impacting human health.

Let me give an example. A particularly toxic pesticide is Aldicarb which has been detected in over 2000 wells on Long Island. Fortunately, it's level in ground water is relatively low. The acute effects, that is exposure to high levels of aldicarb, would cause diarrhea, nausea, vomiting, abdominal pain, profuse sweating, salivating and blurred vision. On the other hand, chronic effects of aldicarb, that is effects of long-term exposure to small amounts, appears to be negligible.

Question #4: How big a problem are pesticides in our drinking water?

We could say that the threat of pesticides in water is like a small, dark cloud on the horizon which could become a huge, menacing thunder cloud in the future if we don't move quickly to intercept it. The use of pesticides tripled between 1950 and 1980 from a use of 400 million pounds in 1950 to a use of 1.4 billion pounds of pesticides in 1980.

To date, 22 pesticides have been detected in the wells of the United States and it is estimated that another 80 have potential of moving into our ground water. Pesticides have been found in the groundwater of 22 states. As mentioned, Long Island is one of the worse. On Long Island, 13 pesticides have been detected at least once and 8 have been found multiple times.

One of the problems has been that our laboratories have not been equipped to detect many of the chemicals that have seeped into our water supply. During the last decade, laboratories have greatly improved their ability to detect these chemicals.

In Bedford, Massachusetts, in 1978, a lab worker happened to bring a sample of his tap water to work where he was testing a new instrument. He discovered 9 toxic organic chemicals in the town's groundwater! The town's water supply wells were shut down permanently. Eventually the contamination was traced to several local industries that were improperly disposing of their chemical wastes.

Question #5: How can I know if there are pesticides in my drinking water?

Some pesticides are regulated by the Environmental Protection Agency (EPA) and a Maximum Contaminant Level (MCL) has been set. For these, public water systems are required to conform to the standard set by the EPA and are required to inform you, the consumer, if and when the level of contamination is higher than the standard given. If the level of the pesticide is below the MCL, this means that it is at a level where there are no negative health effects.

It should be noted that the EPA is currently reevaluating all pesticides registered before 1972 to update them in line with modern health standards. It is also true that many of the pesticides in use today have not been regulated. The EPA has been given the authority to regulate them, but the task of determining which ones need to be regulated and what is the safety level, let alone how to measure the chemical level and its health effects, all go together to make it a daunting task.

Questions #6: How would I go about removing pesticides from my drinking water?

The kind of filter that is best suited to reducing pesticides to safe levels as well as other organic chemicals and compounds from your tap water are carbon filters. Distillers can reduce non-volatile chemicals, but can't remove the volatile kind. However, even with carbon filters, you need to check the individual filter that you are considering to not only see if they claim to reduce pesticides, but to verify that it has been certified by the NSF International as a filter that does indeed effectively reduce them.

The complication here is that there are so many pesticides and even more synthetic organic chemicals, and only a relatively small number are tested for and even less have a standard level of safety assigned to them (MCL). For example, Denver Water, the company that supplies much of the water to the city of Denver, tests for 73 different pesticides of which only 23 have been assigned MCLs by the Environmental Protection Agency (EPA).

It is particularly disconcerting to know that of the thousands of synthetic organic chemicals in use, Denver Water tests for only 150 and much fewer than this have been assigned a Maximum Contaminant Level (MCL) by the EPA.

For further information on the best filters in the category of Filtration go to "Best Water Filters". Or for a broader discussion of the multiple considerations you need to keep in mind in selecting a filter, go to "How to Choose a Water Filter".

For more information about pesticides and other toxic contaminants, go to "Pesticides in Water".

SUMMARY TABLE