Dear Johannes,

there is a study by Peirce on salt tolerance of sheep, especially the tolerance of sheep for sodium chloride in the drinking water that may be of assistance

http://www.publish.csiro.au/paper/AR9570711

Another relevant study may be the non-accidental salt poisoning study

http://adc.bmj.com/content/68/4/448.short

Trust this helps

FC

Hi Johannes,

I guess you found most of these papers already but these is what I found found about the topic with a quick search through google and google scholar:

- Laell et al. 1944, DESERT CLIMATE PHYSIOLOGICAL AND CLINICAL OBSERVATIONS. The Lancet 244, pp. 491-497

http://www.sciencedirect.com/science/article/pii/S0140673600742097#

- Gleibermann, L. 1973, Blood pressure and dietary salt in human populations. Ecology of Food and Nitrition 2 (2) pp. 143-156

This one seems to compare the effects of salt intake in different human populations but since I can not directly asses it I don't know whether it only takes sodium into account or if chloride is also dealt with.

http://www.tandfonline.com/doi/abs/10.1080/03670244.1973.9990329#preview

- Stevenson, Richard J.; Case, Trevor I.; and Oaten, Megan J. 2010, Salt-Induced Thirst Results In Increased Finickiness In Humans. The Psychological Record: 60 (3), Article 1.

http://opensiuc.lib.siu.edu/tpr/vol60/iss3/1

This one is about increased finickness in humans under thirst conditions.

I hope one of these proves usefull. I will probably look up more later.

Excessive salt (sodium chloride, NaCl) intake can lead to the condition known as salt poisoning, salt toxicity, hypernatremia, or water deprivation–sodium ion intoxication. The last term is the most descriptive, giving the result (sodium ion intoxication) as well as the most common predisposing factor (water deprivation.) Salt poisoning is unlikely to occur as long as sodium-regulating mechanisms are intact and fresh drinking water is available.

Salt poisoning has been reported in virtually all species of animals all over the world. Although salt poisoning has historically been more common in swine (the most sensitive species), cattle, and poultry, there are increasing reports of adverse effects in dogs from acute excess salt consumption. The acute oral lethal dose of salt in swine, horses, and cattle is ~2.2 g/kg; in dogs, it is ~4 g/kg. Sheep appear to be the most resistant species, with an acute oral lethal dose of 6 g/kg.

All of you,

thank you for your fast reply! I want to add some further explanation to my question: For me it is important, what is the maximum of water salinity humans can survive some time (couple of days up to weeks or even longer ) without having an alternative freshwater source. I guess in groups which have been confronted with brackish water resources for generations without alternatives (wetlands under hyper-arid, arid and semi-arid conditions) have some kind of physiological adaption different from the median values of caucasian-type humans on which most of the studies are based on. From reindeers I know they can deal with waters of marine salinity over some time, but only from populations adapted on cold arid environments for a lot of generations.

Dear Mr. Prinsloo,

thank you for your paper suggestions. Especially the giving sodium concentrations  of the blood from the second paper are maybe helpful, but unfortunately there are no values for the absolute intake of salt.

Hi Jens,

thank you for your suggestions. I try to find some references before by myself. Two of the ones you mention I have found by my own, but, unfortunately, they are not really helpful. The last psychological study you mention I haven't find by my own, and it is very interesting, but unfortunately they get the result humans didn't take the risk of less water quality and try to find or wait for a better one, which is not applicable for humans at a brackish oasis in a desert environment, far away from the next freshwater source.

Dear Mr. Tepe,

thank you  very much for giving a literally citation from the Merck Veterinary Manual (http://www.merckmanuals.com/vet/toxicology/salt_toxicity/overview_of_salt_toxicity.html) and putting the point on the importance of duration of saline water intake and the availablity of fresh water. This helps me a lot of refining my question. In my model, no freshwater source is available and water is in oligohaline to mesohaline range. Brackish waters (0,5-3 g/l) are generally avoided for drinking (from my small experience), and have no idea how and how long human physiology can deal with that concentration under hot arid environments. And unless the acute lethal dose of salt of a lot animals is known, I did not find anything about humans (except the study mentioned by Mr. Prinsloo above).

Best regards

Johannes

Hi Johannes,

I'm back with a few more papers related to the topic and your specific question:

- Hubbard et al. 1984, Voluntary dehydration and alliesthesia for water. Journal of Applied Physiology 57 (3), pp. 863-873

http://jap.physiology.org/content/57/3/868

This paper deals with the reaction of humans subjects to different water sources (1: tap water (Natick, MA), n = 8; group 2: tap water treated with standard military issue iodine tablets, 8 mg/ 1 (Wisconsin Pharmacol, Milwaukee, WI), n = 11; and group 3: tap water treated with iodine tablets and a commercially available cherry-flavored beverage powder mixed at one-half strength, n = 10. Major ingredients were citric acid, -6% sucrose, monocalcium phosphate, ascorbic acid, and artificial flavoring and coloring.) and temperatures on a simulated desert walk (14.5 km). It mostly concentrates on the psychological and physiological reasons for voluntary dehydration and the effects of exercise under hot arid conditions (humidity 32%, and wind speed 1.2 m . s^-1 Each subject spent 6 h in the climatic chamber on each of 2 nonconsecutive days. During the test subjects

walked on one of two treadmills) but probably some of the information in there proves useful to you.

- Jackson, F.L. 1991, An evolutionary perspective on salt, hypertension, and human genetic variability. Hypertension 17 [suppl I]:I-129-I-13

http://hyper.ahajournals.org/content/17/1_Suppl/I129.short

This paper is more about the genetic effects of the passage of the ancestors of african-americans over the Atlantic Ocean, but probably there is something in there you can use as a rational about certain kinds of physiological stress and genetics human populations (although this seems to be more about tolerance for a general lack of water and salts creating a bottleneck).

- Frisancho, A. R. Human Adaptation and Accommodation. University of Michgan 1993 [org. 1939]

http://books.google.de/books?id=-K_SYHBo42MC&lpg=PA3&ots=QUz4q0uqXX&dq=salt%20water%20intake%20tolerance%20human%20population%20physiological&lr&hl=de&pg=PA53#v=onepage&q=salt&f=false

There is a chapter about theroregulation under heat stress in different populations (page 53 and following), but unfortunately it is mostly about body temperature and water loss, not about the tolerance for higher water salinity

- Paque, C. Saharan Bedouins and the Salt Water of the Saharah: A Model for Salt Intake. In: Biological and Behavioral Aspects of Salt Intake, eds.: Kare, M., Fregly, M.J., Bernard, R.A. 1980 Academic Press inc., (18? pp.)

http://books.google.de/books?hl=de&lr=&id=W3L8W9mLC7MC&oi=fnd&pg=PA31&dq=saltwater+intake+tolerance+human+population+physiological+arid&ots=X9pzTC8vEm&sig=0P6yzstHTpvmnOB38VBznUE7lQ8#v=onepage&q&f=false

I guess this chapter is the kind of paper you've been looking for.

I have no academic expertise in this area.  I can add some context based on my experience as an hiker in arid environments.  If one is active under hot environmental conditions, one can pretty much live on Gatorade (although it is not optimal).  Gatorade is about 1g/L NaCl.  From this I would conclude that a human could survive indefinitely on 1g/L TDS water if one is perspiring significantly. 

The question about sulfates is a separate issue that isn't addressed by this.  My guess is that most healthy humans could adapt to concentrations of sulfate  significantly greater than > 0.25g/L (the EPA drinking water guideline) even though many people might suffer some digestive problems when abruptly switching to 0.5g/L sulfate in water from a normal diet of typical US tap water.

I don't know how far above 1g/L TDS some populations might be able to go, but I wouldn't want to try it personally.

I have been in this field for a while and have researched into freshwater scarcity and desertification. Unfortunately, there are no extensive research in this area of your question although some people have shown interest in the past. I'll reckon the best would be to adapt from some of the publications already mentioned e.g. Hubbard et al. 1984 and the last comments. This obviously will open up a new research study for some and an opportunity to follow up our previous interest with quantitative studies. All the best.

Dear Mr. Adelana and Mr. Mabey,

thank you for your answers!

Dear Jens,

thank you very much for your additional references, especially the last one is great and exactly the kind of information I was looking for.  I ordered the whole book immediately. I owe you a beer!

Best regards

Johannes

Great to hear you're sorted. Let's know when you publish on this aspects. Kind regards,

Michael

Dear colleagues,

you will find the discussion of saline water intake by early hominins (and recent desert inhabitants) as an additional issue of our palaeoenvironmental paper "The spring of Nadaouiyeh Aïn Askar – Paleoecology of a Paleolithic oasis in arid central Syria." published in Palaeo3.

Link (only the uncorrected proof is available at the moment): http://www.sciencedirect.com/science/article/pii/S0031018216000316

Enjoy reading.

Best regards

Johannes