BS: Litre % vs. ppm

Subject: BS: Litre % vs. ppm
From: Ebbie
Date: 13 Nov 06 - 11:59 AM

"The Clinical Toxicology of Commercial Products, 5th Edition (1984), gives lead a toxicity rating of 3 to 4 (3 = moderately toxic, 4 = very toxic) and the EPA has set 0.015 milligrams per liter as the MCL for lead in drinking water - with a goal of 0.0 milligrams per liter. The toxicity rating for fluoride is 4, yet the MCL for fluoride is currently set at 4 parts per million, over 250 times the permissible level for lead." From today's Letter to the Editor. Juneau Empire


This is an easy question for most folks, I imagine, but not for me. So: How does one measure parts per litre against parts per million?

Subject: RE: BS: Litre % vs. ppm
From: MMario
Date: 13 Nov 06 - 12:06 PM

1 gram = 1 cubic cm (roughly) so there are a thousand in a liter.

1 milligram is 1/1000th of a gram - so 1 milligram = 1 ppm in a liter.

the thing is you can't compare just the toxicity - you have to factor in things like what percentage is retained in the body - where it is deposited in the body - etc.

Subject: RE: BS: Litre % vs. ppm
From: bobad
Date: 13 Nov 06 - 01:04 PM

Parts per million ("ppm") denotes one particle of a given substance for every 999,999 other particles. This is roughly equivalent to one drop of ink in a 150 litre (40 gallon) drum of water, or one second per 280 hours. One part in 106 � a precision of 0.0001%.

A milligram is a thousandth of a thousandth, or a millionth of a kilogram. A milligram is one part per million of a kilogram thus, one part per million (ppm) by mass is the same as one milligram per kilogram. Just as part per million is abbreviated as ppm, a milligram per kilogram has its own symbolic form -- mg/kg, which unlike ppm is unambiguous.

http://en.wikipedia.org/wiki/Parts_per_million

Subject: RE: BS: Litre % vs. ppm
From: GUEST
Date: 13 Nov 06 - 01:12 PM

http://en.wikipedia.org/wiki/Gram_per_litre

Subject: RE: BS: Litre % vs. ppm
From: Ebbie
Date: 13 Nov 06 - 02:25 PM

I'm a word person and much as I would like it not to be so, when I read math equations my mind blurs. I thank you all for the impressive information but unless you were here diagramming it for me I'm just not going to learn much.

So my question remains: What is the conversion of parts per litre to parts per million? I just barely recognize that the equation has to be reduced to the same basis.

Further, is the writer correct that 4 ppm is "more than 250 times that of .015 per litre? Quote: "The toxicity rating for fluoride is 4, yet the MCL for fluoride is currently set at 4 parts per million, over 250 times the permissible level for lead."

Subject: RE: BS: Litre % vs. ppm
From: pdq
Date: 13 Nov 06 - 02:51 PM

TOXICITY RATING:


Very Low (1)

PEG = 100 ppm or 10 mg/m3


Low (2)

PEG = 50-100 ppm or 5-10 mg/m3


Moderate (3)

PEG = 5-50 ppm or 0.5-5 mg/m3


High (4)

PEG = 0.5-5 ppm or 0.05-0.5 mg/m3


Very High (5)

PEG < 0.5 ppm or 0.05 mg/m3

Subject: RE: BS: Litre % vs. ppm
From: gnu
Date: 13 Nov 06 - 02:55 PM

Microlitre. One millionth of a litre.

Subject: RE: BS: Litre % vs. ppm
From: MMario
Date: 13 Nov 06 - 03:10 PM

two hundred and sixty-six and 2/3rds times.

for all essential purposes milligrams per liter and parts per million may be considered to be equal. There are other factors to consider - but for general purposes that will do.

Subject: RE: BS: Litre % vs. ppm
From: JohnInKansas
Date: 13 Nov 06 - 04:03 PM

The units used in the reference differ because in each case the units relate to the different methods customarily used for measuring the "amount" of the toxin in question in public water supplies.

In many cases a difference can be equivocated by noting the enormous difference in the molecular weight of two toxins. For many substance it's the "number of molecules" that the body absorbs and retains that's most significant, so a much larger "amount" in grams of a high molecular weight substance like lead is required to get the same effect than is needed for substance with a very low molecular weight like fluorine.

The real difference in this case, however, is that lead is "toxic" in any amount, and since it is not significantly eliminated by normal body processes it accumulates over time with rather low but continuous exposure.

Some minimal presence of fluorine (fluoride) is necessary for good health. The benefits for prevention of tooth cavities are much debated, not with respect to the need for some but on the amounts needed; but benefits for maintaining of bone mass - prevention of osteoporosis and other age-related bone glacility - are well demonstrated.

Fluorine/fluoride begins to be toxic only after a fairly substantial basal-body-content is exceeded. Fluorine/fluoride in excess of body needs also is naturally removed at least partially by normal excretion so that it accumulates less rapidly, although the ability of the body to maintain appropriate levels in the presence of excessive input exposure is limited.

In both cases, the limits cited are levels that are acceptable for long term exposure to the two substances. Quite different numbers apply to the amounts retained in a person that will produce toxic effects.

The water standard for lead assumes that once a person ingests lead it remains in the body permanently, so the standard must be low enough to prevent significant adverse toxicity over a lifetime of exposure, from water and all other kinds of exposure.

The water standard for fluoride needs only to prevent ingestion at a rate that exceeds the rate of excretion (with some allowance for other sources of fluoride ingestion).

Lead is like your favorite rat poisen. Any amount is dangerous.

Fluoride is more like your favorite mood enhancer. Some helps, but an "overdose" will kill you. The standard must allow for mainenance of "good levels" without producing "toxic levels."

The numbers cited appear to be good enough, but the comparison, in the way it's expressed, is an apple-to-oranges comparison with the result expressed in units of plums.

John

Subject: RE: BS: Litre % vs. ppm
From: GUEST, Ebbie
Date: 13 Nov 06 - 07:21 PM

Hey, thanks, guys! I think that I'm getting it. When MMario said that about their being roughly equal the rest fell into place.

Above optimum doses many medications are toxic. Rat poison is the active ingredient in some prescriptions, for instance. For that matter, common table salt is poisonous. Oh, and there is such a thing as WATER poisoning. Ya cain't win.

As for the question at hand, I know the man who wrote that letter to the editor and I wanted an idea of the validity of his argument. I'm not convinced of the utility or feasibility or necessity of fluoride-enhanced water; on the other hand, children today have much better teeth than do previous generations...

Subject: RE: BS: Litre % vs. ppm
From: The Fooles Troupe
Date: 13 Nov 06 - 07:36 PM

Interestingly,

Re Fluoride added to water supplies - when the manufactures of Aluminium, etc began to gather large quantities of this toxic waste byproduct, they 'discovered' that adding it to water supplies improved dental health!

And of course, they get paid for it...


Cynical Robin...

Subject: RE: BS: Litre % vs. ppm
From: Bobert
Date: 13 Nov 06 - 07:45 PM

Well, all this 'rethmizin' give me a headache so I put the Wes Ginny Slide Rule on it but...

Lead is out, out, out... Yeah, used to be that was thwe big boogie stuff in the water...

Now it's ***arsenic*** that is makin' its way into out drinking water that me an' the Wes Ginny Slide Rule is concerned about... Yeah, when Bush says, "No problem", you have a problem...

Bobert

Subject: RE: BS: Litre % vs. ppm
From: JohnInKansas
Date: 13 Nov 06 - 08:29 PM

Much arsenic contamination comes from natural sources, but mining has concentrated and released it in lots of places so that streams below mining areas have suffered a lot of damage. There are also a few industrial dumps that are notorious.

Although it's a little less toxic than the heavy metals, zinc contamination from mining is something of a problem in some areas.

A growing concern is contamination of refuse dump areas with cadmium and antimony, since both have been used in much greater quantities in "modern" storage (and primary) batteries that get dumped where they shouldn't be.

The once very common old practice of melting down old battery plates to recover the lead for hobby uses should now be considered extremely dangerous due to the "other heavy metals," some of which are extremely volatile at "casting temperatures."

Cadmium was once widely used for plating things like refrigerator shelf grids, and they'd occasionally get used as a "grill grid" by the unwary, with really bad effect due to inhalation of the cadmium evaporated at cooking/grill temperatures. So far as I know, most such "grates" now are generally either CRES or chromium plated. I suspect that it's a "regulatory requirement," but haven't checked on it. Chrome is just as toxic as cadmium or lead, but it's a lot harder to ingest, largely due to its high melting point, low volatility, and freedom from corrosion products with "unusual properties." Rhodium is similar to chrome, but is too rare to be used in "bulk products" so it hasn't appeared much as a public concern.

Cadmium is still used for plating a lot of nuts and bolts, so tossing unknown articles in the fire pit still can be somewhat hazardous.

The naturally occuring fluoride in groundwater varies a lot from one place to another. In SW Arizona it's so high that it's unsafe to drink the water. The military bases (Army and Marine) at Yuma AZ probably still provide bottled water for the people assigned/working there to avoid fluorosis, although I haven't checked on them since 40 years ago. Many of the "citizens" in the area did drink the local water, and the effects were obvious. Some places that add fluoride probably have enough naturally appearing that the need for an addition is questionable. "Conspiracy theories" and other objections still prevent adding it in many places where it probably could be of real benefit.

While the allegation that fluoridation is something pushed on people to get rid of an otherwise worthless product, others see it as an instance where medical research found something abundant and ridiculously cheap that could be of benefit. Few on either side seem inclined to change their opinions, so it doesn't merit much discussion (by me, at least).

John

Subject: RE: BS: Litre % vs. ppm
From: The Fooles Troupe
Date: 13 Nov 06 - 09:05 PM

John, it's a bit of Column A, a bit of Column B...

Subject: RE: BS: Litre % vs. ppm
From: JohnInKansas
Date: 14 Nov 06 - 01:46 AM

Can we narrow that to between A_i and B_j^a ?

John

Subject: RE: BS: Litre % vs. ppm
From: The Fooles Troupe
Date: 14 Nov 06 - 07:23 AM

Yes, John, I saw The Matrix...

Subject: RE: BS: Litre % vs. ppm
From: Jeri
Date: 14 Nov 06 - 09:06 AM

Not 'roughly equal', Ebbie - they ARE equal. I also found that the discrepency has been noticed before. http://waterworks4u.com/Fluoride.htm

I knew a woman who'd grown up in New Mexico, and who had never had a cavity. Her village was one that was studied, because nobody who grew up there had ever had a cavity. The study concluded that because fluoride levels were unusually high, it was the fluoride. I think fluoride helps, but there are other factors, and there are likely better ways to get it to people than public water supplies.

Subject: RE: BS: Litre % vs. ppm
From: leeneia
Date: 15 Nov 06 - 09:21 AM

I have a friend from SE Kansas who is one of eight children. There is virtually no fluoride in their well water. The older children all are plagued by teeth which rot from the inside. The younger children are not - because the local dentist told their mother to take fluoride pills when she was pregnant with them.

Subject: RE: BS: Litre % vs. ppm
From: MartinRyan
Date: 16 Nov 06 - 07:33 AM

Mmario's point about the equivalence of ppm and mg/l (or microg/ml. for that matter) is, of course true, for solutions in water. But this is such a specific case that I have always tried to teach students to avoid the ambiguous and stick to the specific.

Regards