Re: Steripen

Dear Mr. Addleton:

I can tell you that we have tested the Steripen against Giardia cysts and 
Cryptosporidium oocysts, and that these organisms were destroyed in our 
experiments.

E.A. Meyer

On Mon, 2 Aug 1999, David F. Addleton wrote:

> Can you confirm you conducted tests for Hydro-Photon's Steripen?
> If you did, can you release the results to me?
> Thanks.
> David Addleton,
> Interested in portable UV water purification.
> 
> See below:
> 
> By the numbers:
> 
> 1 joule/square meter = 16.68 mw-s/10,000 sq cm  =  .001668 mw-s/sq cm
> 
>  
> UV with wavelengths 315 - 400 nm. 
> 
>  
> UV with wavelengths 280 - 315 nm. 
> 
>  
> UV with wavelengths less than 280 nm. 
> 
> Sunlight:
> 
> for a list of articles with abstracts measuring the in situ effect of
solar
> UV light on plankton in high altitude lakes see the following address:  
> 
> The atmosphere filters out most of the solar UV-C. Almost every measure
of
> solar UV I’ve found appears to involve either or both UV-A & UV-B. Ozone
> absorbs a particular wavelength of UV-B, and ozone depletion seems to
> correspond with the amount this wave length UV-B arriving at the surface
of
> the earth. [The steripen uses the more energetic UV-C radiation,
> specifically 254nm. See steripen specs below.] So direct comparison of
the
> steripen with solar UV radiation appears rather difficult.
> 
> See:
>  - offers a uv index for meteorological forecasts to the public. So the
US.
> Here’s how the US calculates the index:  
> Also See:  
>  
>  which provides measurements for UV-A & -B and defines irradiance as
> follows: Irradiance The power transferred to a unit area of a surface by
> radiation from all directions within a hemisphere, measured in watts per
> square meter (W/m²); Irradiation 
> The energy transferred to a unit area of surface by radiation from all
> directions within a hemisphere during a specified period of time,
(measured
> in Joules per square meter (J/m2)) 
> This site provides access to data from a large number of north american
> observation sites.
> 
> The only data I can find appears to measure UV-B radiation in terms of
> joules/meter squared.
> Seasonal variation in intensity in the USA appears to range from 1000 to
> 5000, with the northern latitudes receiving less and southern latitudes
> receiving more.
> 
> J/m2	mw-s/cm2	
> 800	1.3344	
> 1000	1.668	
> 2000	3.336	
> 3000	5.004	
> 4000	6.672	
> 5000	8.34	
> 
> Higher elevations, latitudes closer to the Equator, and clearer skills
will
> allow more UV light of all kinds to reach the surface.
> 
> The literature on the effect of solar UV-B light on in situ bacteria and
> viruses appears to support the idea that long exposure times to solar
UV-B
> will harm these creatures. Most of the studies appear to observe lakes to
> varying depths. Aerated water flowing over stones at higher elevations
> should harm these pathogens sufficiently to make it safe. 
> 
> 3,600 seconds lapse in every hour. Thus when solar UV-B reaches its peak
> around 5000 j/m2, an hour’s exposure will create a dose of just over
30,000
> mw-s/cm2 of UV-B radiation. Human skin will likely burn within 15-30
> minutes at this dose.
> 
> 
> 
> What is necessary in a UV-C lamp to kill pathogens:
> 
> >From  
> 
> Due to individual cell makeup, different levels of UV energy are required
> for destruction. UV lamps emit about 90% of their radiated energy at
253.7
> nm, which, by coincidence, is very close to the peak germicidal
> effectiveness of 265 nm.
> 
> The degree of microbial destruction is a product of both time, which is
the
> actual residence, or contact time the water is within the sterilization
> chamber, and intensity, which is the amount of energy per unit area
> (calculated by dividing the output in watts by the surface area of the
> lamp). This product of intensity and time is known as the Dose and is
> expressed in micro watt seconds per centimeter squared (micro w sec/cm1).
> 
> DOSE = output (watts) x time (sec)
> ------------------------------------------
> area (cm1) = micro W sec / cm1
> 
> Microorganism Destruction Levels
> (Ultraviolet energy at 253.7 nm wavelength required for 99.9% destruction
> of various microorganisms - in micro w sec/cm2)
> Bacillus anthracis	8,700 	Shigella dysentariae (dysentery) 	4,200 	
> Corynebacterium diphtheria 	6,500 	Shigella flexneri (dysentery) 	3,400 	
> Dysentary bacilli (diarrhea) 	4,200 	Staphylococcus epidermidis 	5,800 	
> Esoherichia coil (diarrhea) 	7,000 	Streptococcus faecaelis 	10,000 	
> L.gionelia pneumophlila 	3,800 	Vibro commo (cholera) 	6,500 	
> Mycobacterium, tuberculosis 	10,000 	Bacteriophage (E. coli) 	6,500 	
> Pseudomonas aeruginom 	31,900 	Hepatitis 	8,000 	
> Salmonella (food poisoning) 	10,000 	Influenza 	6,800 	
> Salmonella pamfyphi (enteric fever) 	6,100 	Polloviws (poliomyelitis) 
> 7,000 	
> Salmonella typhosa (typhoid fever) 	7,000 	Baker's yeast 	8,800 	
> 
> steripen specs: see  
> 
> Battery - AA size lithium-metal, 3.2 volts, 900mA hrs., rechargable, 250+
> charge cycles.
> 
> Lamp Assembly - Lamp body and outer jacket are made from UV grade fused
> silica (quartz). lamp assembly is .51" diameter and 1.925" in overall
> length.
> 
> Lamp Output - Lamp is a 5 watt low pressure fluorescent with a primary
> UV-"C" output of 254 nano-meters.
> 
> Electronics - Circuit provides 850 VAC start-up voltage and 270 VAC
> operating voltage. Nominal operating current is 16mA. An ultra-low power
> micro-controller provides features including: automatic variable on/off
> timing, low voltage warning, low voltage shut-down, and "child-safe"
> switching.
> 
> Battery Charging - The LT1510CS on board charging IC is designed
> specifically for use with Lithium batteries. The LT1510C allows for DC
> input voltages between 8 and 29 VDC.
> 
> We don’t need to believe the specs to see why the steripen should
sterilize
> a cup of water in 30 seconds.
> I’m willing to guess, but not bet, that the steripen inventor called up
> this company to design his own lamp for the steripen: . Doubtlessly if he
> didn’t call this one he called a similar one.
> 
> Go elsewhere at this company’s web site to find the methods it uses to
> determine the bulb’s out put. You won’t find the steri-pen’s lamp in its
> stock inventory but you can review the spec sheets for its stock
inventory
> and will find that these lamps send 90% of their output in the 254nm
> wavelength, so they are very well tuned lamps. The company measures the
> output intensity as follows: The output is measured at a distance of
0.75"
> (19.1mm). Emission intensities follow the inverse square law. Thus, UV-C
> light output from the pen should form a cylinder measuring 1.5 inches (+
> what the lamp displaces) in diameter producing the intensity specs
> indicated. I can’t tell from the spec sheet how long the cylinder might
be,
> but it claims nearly 2 inches. 12 oz = your basic coke can which measures
> approx 2.5 inches in diameter 5 inches tall.
> 
> If you assume this tuned lamp produces only 25% of its claimed 5 watts at
> the 254 nm wave length, you have 1,250 mw-s/cm^2 to swish around in a
> volume of clear water not a whole lot larger than the pen itself. Do it
for
> 30 seconds and you’ve doubtlessly exposed whatever is in that water to
> 37,500 dose units. Pseudomonas aeruginom requires a dose of 31,500 to
knock
> out.
> 
> If the lamp operates as this manufacturer claims it should, at 90%
> efficiency, you’ve got real over-kill going on: 135,000 of the dose units
> @30 seconds.
> 
> The other thing to notice when comparing solar radiation to UV-C lamps:
> these relatively low power lamps produce significantly more UV-C than
ever
> reaches the ground from the sun; the less germicidal UV-B measured for
> sunburn purposes by meteorologists produces significantly less power than
> the steri pen lamp which would appear, given the inverse square law,
quite
> safe for anyone to use.
> 
> If I’ve missed something here, please explain it to me. But it seems to
me
> that these estimates – and that’s all they are – would explain why the
> steripen should work to sterilize water, and why we can in some places
I’ve
> previously described assume that solar UV has purified a mountain
stream’s
> water.
> 
> 
> 
----------

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