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Andy PhD DABT, Toxicologist
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Experience:  Board certified with 20 years in research or consulting
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I have a toxicology question of series of questions. First,

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I have a toxicology question of series of questions.
First, does anyone know if arsenic as meassure by ug in the urine has a LD50? If so what is it? I was tested for lead poisoning an had a urine test which showed a urine arsenic level of 270 ug.
Is there anyway to determine what my arsenic level was when I took the product which I believe was contaminated with arsenic ( it was a dietary supplement).
I took the product on Oct 19 but did not get a urine test for arsenic until Nov. 14, 26 days later.
Can you estmate what the level would have been on October 19 if the level 26 days later is 270 ug of arsenic by urine testing?
How would the level estimated for October 19 compare with the LD 50 level if such a comparison could be made.
I also had a follow up urine test for arsenic on Feb 24 and it was tested as 18ug of arsenic per day as my background level.
What does a backgrund level mean?
Thank you very much for any help you can provide.
Chris Grell
Hi , I am the Moderator for this topic. I sent an Email to a Professional Toxicologist, when he comes back on like he will see this question. Thank you for your continued patience:-)
Customer: replied 5 years ago.

Dear Camille;

Thank you for the resply. Do you have an estimate of when I might expect to hear back from the toxicologist.


Christopher E. Grell

Hi Christopher, I am sorry but I do not, he is not currently logged on. But you don't have to sit and wait.....we will send you an email notification when your question has been answered.
Customer: replied 5 years ago.

I thought you meant he was away like in terms of days or weeks. I can wait and do not worry, I will not be sitting by my computer screen. I know how doctors are :)



Thank you very much for your continued patience:-)
Hello Chris,
I am a board certified toxicologist, I can answer you questions. I do have a few questions for you to answer as well. Did you, or are you now experiencing any symptoms, such as pain in your feet, cold hands, or vomiting and diarrhea? Do you eat seafood or have well water?
I am assuming the 270 ug of arsenic you are talking about is either from a 24 hour urine sample or is in units of ug/L. Levels below 30ug/L, or 50ug total in a 24 hour sample, are considered background or normal levels. So your current levels of 18ug/L are not considered toxic.
As for your earlier arsenic levels, unfortunately you can't compare them to a LD50 value. A LD50 is obtained in animals and is the dose given to the animals that cause 50% of them to die. Since 50% of the test subjects die at the LD50, you can't test it in humans and the value is reported as a dose that is given to the animals, not as a urine level. However, in studies with workers who are chronically exposed to arsenic, urine levels of above 100ug/L have been seen in workers with symptoms of chronic arsenic poisoning, such as fingers that are cold and possibly bluish in color because of poor blood circulation. However, since you think you were exposed from a dietary supplement then your exposure would be short term and would likely cause problems of the gut, like vomiting or diarrhea. You could also possibly experience pain of the feet.
Arsenic does not stay in the body for very long, it is pretty much gone in less than a week. It is not really possible to back calculate to try to figure out how much arsenic you were exposed to originally since there is so much variability in determining that. Since most is eliminated in less than a week it seems that either you were exposed to a really big dose, or you were exposed to arsenic from another source other than the dietary supplement. Seafood can have high levels of arsenic and in some places ground water has high levels of arsenic. If you have well water that could be a source of arsenic. However since your levels are now well within the normal levels, it probably was a temporary exposure and not from well water which you would be constantly exposed to.
Some symptoms can be delayed and do not show up until a few weeks after you were exposed. However, if you did not experience any symptoms before when you had much more arsenic inside you, then you probably will be fine and would have shown signs of toxicity by now.
Please let me know if you need me to clarify anything and let me know if you have or had any symptoms.
Take care,
Andy PhD DABT, Toxicologist
Category: Health
Satisfied Customers: 137
Experience: Board certified with 20 years in research or consulting
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Customer: replied 5 years ago.

In your reply you sate that to have a 24 hour urine level of 270ug arsenic 26 days later, you would have to have had a "really big dose? Can you estimate or questimate what the really big does might be to get a 270 ug test rsult 26 days later..

Also, what is the likelihood of any of the arsenic consumed 26 days before the test still contributing to the test results of 270 ug done 26 days later? Any estimate or reasonal guess? Say greater than 51 % 90% likely or unlikelyetc?

Can you estimate or questimate how high is high. In otherwords, how does the average background level compare to a 270 ug level.

Is there any info on how high the urine level would have to be to cause death or could cause death. In otherwords, how close would an arsenic urine level of 270 ug be to a potential fatal does. Again any estimate or questimate?.

What is the LD50 for arsenic?

Thanks very much for the anwers you already provided. They are very helpful in figuring out things. If I can get possible answers to the remaining questions, it would be great.

Please let me know .

Thank you


Hi Chris,
Sorry for getting back to you so late, I was out of town for Easter weekend.
You want me to try to estimate how much you were exposed to originally, realize that is just a guesstimate, there are lots of variables in calculating how much you were exposed to originally. I did a simple estimate as follows. If I use an estimated half life of 60 hours and calculate back 26 days, or 10 half lives, then you get about 270 mg for the 24 hour urine test, or 1,000 times higher. Death has been reported to occur in humans from single doses of 100 to 300 mg, which means that my estimated dose would have been a lethal dose or close to it. Since you are still alive either my calculation is vary far off, which could easily be the case, or you are exposed to arsenic from another source. I can't give you a percent likeliness that the 270 ug was from the dietary supplement or from 26 days earlier, but I can say that I do question if it was from the dietary supplement since the half life is only 60 hours. So I do wonder if you are exposed to arsenic from another source. Your best hope in connecting this to the dietary supplement is to have the dietary supplement tested for arsenic. For that you would have to find an analytical lab, possibly a local university would do it too. If you have experienced any symptoms then you could contact the FDA and tell them that you think it was adulterated with arsenic (; I have never done this, but I would imagine that the FDA would test the dietary supplement for you.
LD50 levels have been reported as 150 mg/kg in mice and 700 mg/kg in rats, with as little a 4 mg/kg causing mild toxicity in human children. It isn't possible to convert these to urine levels since there are many variables involved that can change the value, also as you can see there is some variability depending on the species that was tested, i.e. mice vs rat, which mean variability in mice or rat vs human.
I think your best indicator as to how much you were exposed to is if you had any symptoms.
So please answer the following questions:
Did you have any symptoms?
How much of the dietary supplement did you take and did you take it once, or daily and if daily, how long have you been taking it?
What is your occupation?
Do you have well water?
Do you eat lots of seafood?
Do you use arsenic containing pesticides?
Take care,