Toxins in Water-Pesticides and Herbicides
Welcome to the third week of my blog series about toxins in water! If you missed the first and second week,we talked about the types of contaminants that can be in water and why pesticides and insecticides are in our water.
This week, we are going to talk about pesticides and herbicides and the potential health risks they pose.
What pesticides might be in your water?
To find this out, simply check out the EWG’s website. You can enter your zip code and it will tell you which pesticides have been found in you water.
Depending upon where you live, the pesticides that may be in your water differs. According to a 2006 report by the U.S. Department of the Interior, U.S. Geological Survey :
In agricultural areas, the most frequently detected herbicides were those used for agriculture—atrazine, metolachlor, cyanazine, alachlor, and acetochlor.
In urban areas, the herbicides—simazine, prometon, tebuthiuron, 2,4-D, and diuron and the insecticides—diazinon, chlorpyrifos, and carbaryl—were most frequently detected.
Two facts that I read in the report that were frightening were:
“At least one pesticide was detected in water from all streams studied.”
“Of the 178 streams sampled nationwide that have watersheds dominated by agricultural, urban, or mixed land uses, 56 percent had one or more pesticides in water that exceeded at least one aquatic-life benchmark.”
Do these pesticides pose any risk to humans?
According to the report cited above
“Less than 10 percent of NAWQA stream sites and about 1 percent of wells had concentrations greater than a human-health benchmark.”
But what’s a benchmark?
“Benchmarks are estimates of the concentrations above which pesticides may have adverse effects on humans, aquatic life, or fish-eating wildlife.”
The problem with these benchmarks are that long-term studies have not been done to access the effects a low-dose chronic exposure could have on humans.
What have these pesticides been linked to in the lab?
As with all potential toxins, it is hard to model a low-grade, chronic exposure in the lab. That being said, here are some studies:
- Atrazine (ATZ)- shown to affect steroid hormones and interfere with sex pathways critical for development. It was shown to produce a feminization in male mice as well as alterations in learning(source)
- Alachlor– shown to cause liver and kidney abnormalities in Nile tilapia at acute and subchronic doses (source)
- Acetochlor– shown to increase the metabolism and excretion of thyroid hormone as well as cause thyroid cancer in rodents (source)
- Simazine-shown to cause kidney necrosis and liver and hepatic steatosis in fish in the lab and in the wild (source)
- Diuron-shown to have potential mutagenic, teratogenic, reproductive and carcinogenic effects. Rats treated with diuron demonstrated wide-spread signs of toxicity including reduced food intake and body weight gain, as well as increased organ weights at high concentrations in acute and subchronic studies (source)
- Diazinon– shown to have deleterious effects on neural systems(source) and inhibit brain cholinesterase (source)
- Chlorpyrifos-shown to cause neurobehavioral alterations in zebrafish (source)
- Carbaryl-shown to cause defects on the testes of O. elegans, (source)
Below are some observational studies that have been done linking pesticides to disease:
- Exposure to carbaryl was associated with the incidence of multiple myeloma with borderline significance (source)
- Soft tissue sarcoma development was associated with insecticide exposure (source)
- DDT, simazine and lindane have been linked to prostate cancer development (source)
- Carbamate pesticide use is associated with an increased risk of Non-Hodgkin’s Lymphoma risk (source)
- Recent exposure to DDT may increase risk of liver cancer (source)
Note: DDT is currently banned in the US but it still persists in some environmental samples
What is the government doing about this?
“The NAWQA water-quality assessment serves as a foundation for improving water-resource assessment and management, but major gaps in critical information about pesticides still persist and continue to present challenges to scientists, managers, and policymakers. Some of the most important steps needed to fill gaps are listed below:
- Improve tracking of pesticide use in agricultural and non-agricultural areas, including amounts, locations, and timing
- Add assessments of pesticides not yet studied, including some already in use as well as new pesticides
- Improve assessment and understanding of degradates, including their distribution and potential effects
- Evaluate toxicities of mixtures and their potential to affect humans, aquatic life, and wildlife
- Evaluate the performance of management practices and their effects on concentrations and transport of pesticides
- Improve methods for prediction of pesticide levels in unmonitored areas
- Sustain and expand long-term monitoring for trends”
Check out what pesticides or herbicides may be in your water. If there are a lot of pesticides or herbicides in your water, or if you live near an agricultural run-off, consider using bottled water. And keep in mind, as with as laboratory studies, the results cannot always be extrapolated to humans. So, even if you water does have the above mentioned compounds in it, remember that the doses used in studies are often higher than those experienced by humans. However, the observational studies in humans are still convincing of the health risks posed by the chemicals.
Did you check out your water at EWG? What is in your water?