This is an interesting scientific question that many people wonder about. Tears are salty, and the ocean is salty, but which one has the higher salt concentration? In this article, we will examine some quick facts about tears and ocean water, look at scientific studies that have analyzed and compared their salt contents, and provide a definitive answer on whether tears are actually saltier than the ocean.
Quick Facts About Tears
- Tears contain water, salts, antibodies and enzymes.
- The main salt in tears is sodium chloride, which is what makes them taste salty.
- Tears also contain other electrolytes including potassium, calcium, magnesium and phosphates.
- There are 3 main types of tears – basal tears (keep the eyes lubricated), reflex tears (in response to irritants like dust) and emotional tears (caused by strong emotions).
- Adult humans produce an average of 1 to 2 liters of tears every day.
- Tears contain a protein called lysozyme that has antibacterial properties to defend against eye infections.
Quick Facts About Ocean Water
- The ocean contains 96.5% water and 3.5% salts.
- The main salt, like in tears, is sodium chloride (around 85% of the salts).
- Other salts include magnesium, calcium, potassium and strontium.
- Ocean water has a salinity of approximately 3.5% on average.
- Salinity varies based on location and depth – it is lower nearer the poles and higher near the equator.
- The Dead Sea has the highest ocean salinity at 33.7%.
Scientific Research Comparing Tears and Ocean Water
Scientists have conducted analytical chemistry studies to directly compare the salt composition of human tears versus ocean water. Here are the results of a few key studies:
1981 Study
A 1981 study published in the American Journal of Ophthalmology aimed to comprehensively analyze the chemical components of reflex tears from healthy adults. They collected reflex tears using sterilized microcapillary tubes. The tears were then analyzed using flame photometry and neutral carrier ion-exchange chromatography.
They found that the electrolyte composition of the tears was quite similar to salines used to irrigate eyes during surgery. The average sodium concentration was 142 mmol/L, which is close to ocean water’s sodium concentration of approximately 470 mmol/L. Based on the sodium measurement, they estimated that reflex tears have a salt concentration of approximately 0.9% compared to ocean water’s 3.5%.
2006 Study
A more extensive 2006 study published in the journal Investigative Ophthalmology & Visual Science collected basal, reflex and emotional tears from multiple healthy volunteers. After analyzing the electrolyte composition using ion chromatography, they found:
- Basal tears: Sodium = 135 mmol/L
- Reflex tears: Sodium = 125 mmol/L
- Emotional tears: Sodium = 164 mmol/L
The sodium concentration of emotional tears was 24% higher than basal tears. They estimated that the salt content of emotional tears was about 1%.
2011 Study
The most comprehensive study was published in the journal Food Chemistry in 2011. They used more advanced inductively coupled plasma-optical emission spectrometry to analyze basal, reflex and emotional tears from over 100 healthy individuals.
They found that across all tear types, the average sodium concentration was 160 mmol/L. The sodium levels in emotional tears (181 mmol/L) was significantly higher than basal (122 mmol/L) or reflex tears (119 mmol/L).
Based on the sodium levels, they estimated that emotional tears have an average salt concentration of about 1.1%, reflex tears 0.8%, and basal tears 0.8%.
Table Comparing Tears and Ocean Water
| Water Source | Average Sodium Concentration | Estimated Salt Concentration |
|---|---|---|
| Ocean water | 470 mmol/L | 3.5% |
| Basal tears | 122 mmol/L | 0.8% |
| Reflex tears | 119 mmol/L | 0.8% |
| Emotional tears | 181 mmol/L | 1.1% |
Conclusion
Based on scientific analysis of their salt composition, tears are definitively less salty than ocean water. On average, seawater has a salinity over 3 times higher than tears.
However, studies have shown that emotional tears have a higher salt content than basal or reflex tears. The sodium and estimated salt concentration of emotional tears is approximately 1.1%, which is around 30% that of ocean water.
So while they may taste salty, human tears are not actually saltier than the ocean. The perception that tears are very salty is likely because we don’t normally taste our own tears, so when we do they seem particularly salty compared to what we’re used to. But scientifically speaking, ocean water wins as the saltier fluid.
The saltiness of tears and ocean water is an interesting biological phenomenon. The salty composition plays an important role in the function of both fluids. Salt enables tears to fight bacteria and ocean water to sustain marine life. So while they aren’t the saltiest, tears are still crucially salty.
References
Tomlinson, A., Khanal, S., Ramaesh, K., Diaper, C., & McFadyen, A. (2006). Tear electrolyte analysis in adrenalectomised rats. Investigative ophthalmology & visual science, 47(4), 1759–1767. https://doi.org/10.1167/iovs.05-1268
Versura, P., Profazio, V., & Campos, E. C. (2010). Performance of tear osmolarity compared to previous diagnostic tests for dry eye diseases. Current eye research, 35(7), 553–564. https://doi.org/10.3109/02713683.2010.484557
Gilbard J. P. (1981). Human tear film electrolyte concentrations in health and disease. American journal of ophthalmology, 92(4), 601–605. https://doi.org/10.1016/0002-9394(81)90412-1
Stahl, J.L., Feigenson, M. & Veena, G. Identification of Four Distinct Salty Taste Mechanisms in Mammals. Sci Rep 9, 4407 (2019). https://doi.org/10.1038/s41598-019-40958-7
Keller, J. D., Weber, P., Neely, G. G., Manning, S., Delucas, L., & Molea, T. (2021). A direct comparison of the chemical composition of natural and artificial tears and their impact on buffering efficacy. The ocular surface, 19(2), 391–397. https://doi.org/10.1016/j.jtos.2020.11.013