The Hole Story:
Ozone Depletion Research in the Areas of Medical, Biological and Veterinary Science, Physics, Pharmacy and Physiology

by Sharon Beder



Introduction

Human Studies of Skin Cancer
Sunscreen and Fabric
The Mouse Model of Cancer
Studies Using Skin Tissue
Drugs and Sunlight
Plant and Algae Growth
Conclusion
Glossary

Book Site Map


Sunscreen and Fabric Protection ctd.


Connnection between Sun Burn and Skin Cancer

There are four basic skin types. A person with type 1 skin never tans at all and a person with type 4 wouldn't normally get sunburned at all. They have not used black skinned people in the experiments because the person would have to sit still and be irradiated for so long. If the fabric has an FPF of 20 they would need to sit against the template for 20 times the period of time that it takes to get redness on their skin normally. This could mean that a person with black skin would have to be constantly sitting there for 2 hours. Also it is difficult to see redness with black skin. They tend to test people with type 1 to 3 skin, type 3 being someone who tans more readily than they burn. They, therefore cannot be sure the same protectiveness would occur in black skin. However, since black people are less prone to skin cancer there is less incentive to test them. For example Aboriginals are much less susceptible to skin cancer than white people. Indians are reasonably susceptible but skin cancer is very rare in black skinned populations.

Both sunburn and skin cancer depend on UV radiation dose. In animal tests the greater the dose they are exposed to the more tumours they get. Similar experiments can not be done on humans for ethical reasons but some evidence exists that the same holds true for humans. The best study for this was a comparative study of Anglo Saxon men who did their war service in the tropics versus those who did their war service in Europe during the second world war. There was a statistically significant increase in the tumours in the first group. So it is assumed, based on that work that the more UV you get the more tumours you’re likely to get and it is certainly true in mice.

As noted in the previous section the relationship between redness and skin cancer is not really known. “You can certainly induce tumours in rodents without inducing redness. You can repeatedly irradiate them without them going red, giving them doses that aren’t enough to burn them. So it is possible that a fabric or sunscreen that stops you getting red, mightn’t stop you getting tumours,” Walker points out that “This is one of the unknowns. It is worthwhile making the point that the research is not all cut and dried.”

However the wavelengths of light that cause redness overlap with and are very similar to the wavelengths which cause cancers. For this reason the researchers say that if fabrics are reducing the amount of UV a person is getting then that person has less chance of getting a tumour.


Previously in this chapter:
Introduction

Sunscreen Testing
Sunscreen Labelling Issues
Relations with the Sunscreen Industry
Fabric Protection Factors

Next in this chapter:
Predicting Fabric Protection Factors
Fabric Design


URL: http://www.herinst.org/sbeder/HoleStory/hole.html