Folks,
EPA’s Hazard Summary for vinyl chloride is attached. I thought it would be of interest to this group as a reference, especially after reading the news report below. One glaring mis-statement below (see yellow highlight) is the implication that the water smelled funny, supposedly because it contained vinyl chloride. According to EPA, and ATSDR, the odor threshold for vinyl chloride is 3,000 parts per million. This is extremely high and one can conclude that the water did not smell funny from any presence of vinyl chloride. The vinyl chloride values according to the test reports at the school were measured with the highest at 2.35 parts per billion (ppb) which is slightly over EPA’s 2.0 ppb for drinking water. That means the measured amounts were 1 million times below the odor threshold for humans.
A conclusion could also be drawn that the dog did not smell it either- here is why. Based on the attached NOVA article, dogs have 50 times more olfactory nerve endings than humans and 40 times more brain capacity to analyze smells; I could not find any reference to say exactly how much more sensitive dog’s sense of smell is compared to humans. But using this comparison, it could be correlated to say that dog’s sense of smell is as much as 2,000 times more sensitive than humans. On this basis, it means that the measured levels in the San Diego school water were still 500 times below the odor detection level for the dog. One can conclude from this anecdotal calculation that the dog did not smell vinyl chloride. While it is true that dog’s can detect smells in the parts per trillion levels, that would be for substances that already have a very low odor threshold, which vinyl chloride does not have. Other reports on dog’s sense of smell state:
“Much of the deeper work of trying to understand the sense of smell has been done on humans; how do you ask a dog what he feels or remembers when he smells a certain odor? But we do know that dogs have much more surface area within their nasal cavities, and this area is well supplied with sensory cells – estimates of the total number of these cells vary and depend on the breed, but they have been cited as somewhere between 125 million and several times that. (This compares with estimates of human numbers that are in the 5- to 10-million-cell range.)
In addition, the dog has devoted a tremendous amount of his brain tissue to olfactory cells. (Some estimates allocate one-third of the dog’s brain to the chore of scenting.) All this adds up to a canine scenter that has thousands to millions of times the ability of his human counterpart.” Ref: http://www.whole-dog-journal.com/issues/7_11/features/Canine-Sense-of-Smell_15668-1.html
It is difficult to exactly quantify how much better dogs smell than humans, and it is likely very substance specific as well. But there are enough issues with saying the dog smells vinyl chloride at 2.35 ppb that no one can scientifically corroborate that indeed happened in San Diego without having a specific animal study reference on this specific substance. I hope this information is helpful.
Regards,
Rich
Please find below the most recent piece on the San Diego school issue. There is no mention of PVC pipe in the article but still wanted to share this with the group.
Iris
San Diego Cooperative Charter Offers Parents Free Lead Blood Tests for Students
http://www.nbcsandiego.com/news/local/San-Diego-Cooperative-Charter-Offers-Parents-Free-Lead-Blood-Tests-for-Students-419334114.html
By Wendy Fry
NBC 7
4/12/17
A southeast San Diego elementary charter school that discovered high levels of lead and vinyl chloride in its water plans to bring in a free mobile clinic to test kids for any possible lead exposure.
The contamination was discovered after a therapy dog named “Star” would not drink the water. Charter school leaders say the 2-year-old black lab went to great lengths to alert them to the potential danger in the water.
The San Diego Cooperative Charter School is located on the Emerson elementary school campus at Boston and 36th Street. San Diego Unified District officials discovered lead and vinyl chloride in the water at levels higher than allowed by the Environmental Protection Agency (EPA).
Director Tom Pellegrino said no kids have been sick or reported any symptoms on the charter school side of the campus. However, he said, the charter school leaders are bringing a mobile clinic to the school to test all students for any possible lead exposure “to help put parents minds at ease.” Pellegrino reported the new information to NBC7 and our media partner Voice of San Diego.
One parent told NBC7 on Wednesday the new information did help quell some of her concerns.
“It definitely does put my mind at rest to hear that’s something we don’t have to consider, but I will definitely be checking on my own as well,” said COOP parent Michele Silverthorn.
Silverthorn said she was on her way to her kids’ pediatrician this afternoon for a blood lead level test for her two children who attend the school.
“I’m concerned,” Silverthorn said. “My oldest son has been on this campus for almost two years and he been drinking the water, so we just want to double check that everything is okay.”
Silverthorn said she also planned to ask her childrens’ pediatrician about the vinyl chloride contamination discovered as well.
In February, district officials discovered high levels of vinyl chloride, which they said comes from plastic leeching into the water, and a nurse reported some children were vomiting after drinking the water, which had a reported “funny” smell.
Pellegrino said the reported illnesses were not documented among the 100 or so students that attend the charter school, located on two campuses in the immediate area. Two other San Diego Unified schools are located on adjacent campuses in the same few city blocks.
The SDUSD says it has been providing bottled water to students since the discovery of contamination. The district also hired a consultant for $10,000 to help test the water and take corrective action ahead of scheduled city tests for lead.
Last month, high levels of lead were also discovered in the water on the Emerson campus, which includes the San Diego Cooperative Charter school. Pellegrino said some parents have already taken their students to doctors for tests.
“We have some really good news, which is we have a lot of families who have done the testing on their own and they’ve all reported there have been no increased levels and that’s very heartwarming for us and hopefully that will be the case with the rest of the families that get tested.”
Pellegrino said he recommended the free mobile clinic and other free blood lead level tests to the charter school’s board and funding was approved last night. It’s estimated to cost about $30 per student tested.
Lead was discovered in the water at more than 2.5 times the “action level” for the EPA. The limit is 15 ppb (parts per billion), and once that limit is exceeded the EPA mandates water agencies take action to make sure the drinking water is safe again.
The free blood lead level testing is not part of that required federal mandate, but something the charter school is doing on its own.
“We realize this is going to be the tip of the iceberg in terms of the state of California and the nation for schools. We’re in a new normal for water analysis and it’s a welcome conversation to look at the contaminants,” Pellegrino said. “We’re happy right now that our children have not been affected but we want to make sure we get through all the kids before we take a really deep breath.”
Iris Somberg
Additional Resources
San Diego Water_Initial_Contaminant_Results_Newscenter_SN_03-31-17
NOVA Dog Sense of Smell 10-04-12
Vinyl chloride Hazard Summary Technology Transfer Network Air Toxics Web site US EPA 10-27-15
