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Absorption of Toxic Substances Through the Skin

2004

I have been working in a captive plating shop for about eleven years. The following is a question that was asked in a vegetable seed company's electronic newsletter I read last night. It was in the context of an offering for an oil to be used on tool handles that does not contain any cobalt. The article said that some boiled linseed oil ⇦ this on eBay or Amazon [affil links] offered contains cobalt. This was news to me. Anyway, the question is very general and follows: "What is there to know about how substances are absorbed by the hands?" A complete answer to this question probably requires knowledge in Industrial Hygiene, Immunology, Dermatology, and who knows what else.

I was thinking about this and the following are just a few of my thoughts. I don't want to just post the question without some forethought on my part. Where I am off base, please correct me, add to it, etc. It would be good if some reference could be made to some documenting literature. I am going to email the person that asked this question to tell him to read this question and the responses. I haven't mentioned his name to avoid any commercial endorsements contrary to the rules of this site.

I know that some substances can cause contact dermatitis, which is an allergic reaction. I believe cobalt is one of them. I know nickel is another. In these metals, to cause a reaction in a susceptible individual, they must be present as a salt or other compound. How does the metal salt come into contact with whatever it must come into contact with to cause a reaction? If it just sits on the surface of the skin, without entering the body, how could it cause any problem? (I believe it must contact the white blood cells, where the immune receptors are. I am trying to remember a course in Immunology I took in 1976.) Could it be through small cuts, pores in the skin, ...?

I know that at least in Poison Ivy this is an allergic reaction. The oil, Urushiol, would have to come into contact with our immune system to trigger the reaction. This must mean it is absorbed by the skin. By what means? Through the sweat glands? Dissolving into the skin?

The Merck Index ⇦[this on on Amazonaffil links] says contact with caustic soda ⇦liquid caustic soda in bulk on Amazon [affil link] in the presence of liquids causes damage to the skin by dissolving into the fat and oils of the skin. The same way that soap is manufactured. Lye from wood ashes mixed with animal fats.

Organic solvents are absorbed through the skin and into the bloodstream to be removed by the liver. Do they just pass through the cell membranes and blood vessels? Do they dissolve into the sweat and then through the sweat glands?

I can't think of any other means at the present. Anyone want to help out?

Jerry Smith
Little Falls Alloys, Inc. - Bloomingdale, New Jersey, USA

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2004

No one seems to have taken up your offer. Your subject is incredibly broad and far reaching - there are libraries written on what you ask. To answer it generically, is there not legislation in the US that demands employers tell employees of all the hazards they will encounter whilst doing their job? That should be your first port of call. Secondly, if you have any concerns that your, or anyone else's, health is being jeopardized by your employer, you should go to OSHA or some other authority. However, you must know what you are being exposed to - there is no point in setting a hare loose just to see where it goes! This is a serious subject.

As far as dermatitis is concerned (I am not a dermatologist, so caveat emptor), it is known that nickel can cause eczema as well as dermatitis and other allergic responses. The jury should be out on cobalt because, although it is chemically very similar to nickel, it is an essential element to life and is usually found in conjunction with nickel. Nevertheless, there is some evidence to suggest it may be associated with eczema and other skin related issues, but I stress it is also found with nickel. Other claimed possible irritants are gold and chromium. As far as gold is concerned, this is almost certainly down to bad science. Gold, in its pure state is inert, but to harden it, goldsmiths often add other metals like nickel....Chromium, on the other hand, can be nasty when it is a certain form ("hexavalent chromium"). As far as I know, there is no evidence for metallic chromium being harmful to man.

Metals can manifest their adverse responses in many ways and through many paths. These include soluble salts and fumes from molten metals. Some even have horrible organic complexes that are really quite nasty, but this is such a wide topic, there is nowhere suitable to discuss them.

Metal allergies are not fully understood, but you are wrong to believe the source must be a salt. Most allergies start from things like jewellery - metal in contact with the skin. The skin secretes solutions such as sweat that can dissolve the metals and this creates a soluble salt that can then be adsorbed through the skin into the lymphatic system. The biochemistry of this process is complex and not relevant to this site. Once the allergens are in the lymphatic system, other, more serious issues can arise.

caustic soda ⇦liquid caustic soda in bulk on Amazon [affil link] is also known as sodium hydroxide; it is a very strong alkali that is used in many detergents, soaps, toiletries and cosmetics. It can degrease the skin if it is sufficiently strong and in contact with the skin for sufficient time. Organic solvents cover a multitude of sins - another library has been written about them. They range from ethanol, which many people drink in copious amounts, to benzene or trichloroethane, both of which are not healthy, even in small doses.

I hope this answers your immediate concerns, but if not, I suggest you talk with an occupational hygienist and allay your fears that way.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK

Trevor,

I'll drink to that.

Good discussion!

Trent Kaufman
electroplater - Galva, Illinois
2004

Very interesting discussion! Years ago I was working to remove all SARA 313 listed ingredients from my detergent blends. A supplier's chemist told me EB (ethylene glycol monobutyl ether) was under attack not because it was so harmful to humans as it was such a great penetrant. Whatever was on the skin (grease, dirt, metals) could be taken into the bloodstream along with the butyl solvent. The EB passed through the system and is fairly biodegradable. On the other hand, as I recall, a propylene glycol replacement didn't pass through the human system as well and didn't biodegrade as well. But, it supposedly got a better safety rating.

This info is completely from memory so I may have it backwards. I mention it only to bring up how different materials affect our bodies in different ways. We have penetration issues (solvents) as well as reactions (caustic) and a host of other factors at play. Throw in heat, pressure, variables in skin thickness... it opens up all sorts of questions.

All in all, it is very interesting.

Todd Turner
- Monroe, Louisiana
2004

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2005

 Thanks to all of you that responded to this question. I gave up looking for responses and just saw them today. I ended up contacting an Industrial Hygienist and he emailed me detailed information on the preparation of Linseed Oil for finishing uses. It can contain Cobalt. He didn't think there would be any issues with skin absorption of the Cobalt via contact with oiled wooden tool handles.

I know the question was extremely broad. That is how it was presented in the newsletter. Thanks again for the replies.

Jerry Smith
Little Falls Alloys, Inc. - Bloomingdale, New Jersey, USA