The Heat Index

The heat index tells you how hot it feels outside in the shade. It is not the same as the outside ambient temperature. It combines the humidity with the temperature.  When you are standing in the open and full sunshine the heat index is even higher. A heat index of 90 or greater is considered dangerous.

Sunburn, Sunscreen and How to Avoid Damaging Ultraviolet (UV ) Light

Summer has arrived and individuals are outside trying to obtain the perfect tan.  Exposing yourself to the sun allows your skin to be exposed to ultraviolet light. We are most concerned about ultraviolet light in UV-A spectrum (320-400 nm) and the UV-B spectrum (290-320).  UV-A rays penetrate deeply and cause skin damage including photoaging of the skin, immunosuppression both locally on the skin and systemically and increased risk of cancer and infection. It is the UVB radiation that causes tanning.  The delayed tanning that occurs 3 days after exposure is due primarily to UV-B radiation and is due to a redistribution of melanocytes and new melanin synthesis and formation. This delayed tanning is at best mildly protective against sunburn SPF 2-3 but has no effect on protecting against cancer or photoaging.

Sunscreens can help reduce your risk of developing skin damage and cancer.  Sunscreens are either inorganic containing products that physically shield and block the effects of ultraviolet rays or organic compounds that physically absorb the ultraviolet rays. You should be looking for a sunscreen that is “broad spectrum” protecting against UV-A and UV-B rays.  You want a sunscreen that is substantive.  “Water resistant” products protect up to 40 minutes after water immersion.  “Very water resistant” products protect up to 80 minutes after water immersion.  Data and research shows that a broad spectrum sunscreen with SPF 17 or greater will provide protection against squamous cell carcinomas and photoaging but are less effective in preventing basal cell cancers and melanomas.

It is recommended that we use sunscreen daily on all sun exposed skin. The clouds only scatter UV-B Rays so on cloudy days you are being bombarded with UV-A rays despite it appearing to be overcast.  It will require about a shot glass worth of sunscreen to protect the most sun exposed areas (two tablespoons) which are the face, ears, hands, arms and lips. You should be using an SPF of at least 30 which should be applied 15-30 minutes BEFORE sun exposure.  It should be reapplied every two hours and after swimming or heavy perspiration.

  • Remember that the sun’s rays are strongest between 10 a.m. and 4:00 p.m.
  • Water, sand and, in the winter, even snow reflect UV radiation so be extra careful in those environments.
  • Wear protective clothing such as closely woven, natural fiber, long sleeve shirts and pants, sunglasses and wide brimmed hats.
  • Do not use tanning beds.
  • Do not expect sunscreens to allow you to spend more time in the sun. Long exposure to the sun’s damaging UV rays increases your risk of skin cancer and photoaging.

Summer means longer days and more time spent outside. Be prepared and protect your skin from damage and injury.

What is SPF “Sun Protection Factor” and What is the Daily UV Index?

SPF is a laboratory measure of the efficacy of sunscreen and is defined as the amount of ultraviolet radiation needed to produce sunburn on protected skin relative to unprotected skin. It is a measurement of redness or “erythema” and is mainly a measure of UV-B radiation exposure not UV-A (the more damaging type of radiation to deep skin structure) exposure.

The SPF of a product is not related to the duration of UV radiation exposure. The relationship between SPF and UV-B radiation protection is not 1:1 or linear meaning that an SPF 30 does not protect you for twice as long as an SPF 15.  For example, an SPF of 15 can filter 94% of the suns UV-B radiation while a SPF of 30 will filter 97%. UV radiation dosage depends on both how long you are out in the sun and how intense the UV radiation is.

The daily UV index is a measure of the level or intensity of UV radiation. It is presented on a scale of 1 (low) to 11+ (extremely high). The US National Weather Service and the US Environmental Protection Agency provide this data which is presented on most weather reports and published in newspapers and on line daily.