ARM2.950118.026

CONTROL OF LASER HAZARDS AND MANAGEMENT OF ACCIDENTS

Samuel Fine, M.D.* Edmund Klein, M.D.** George R. Peacock* Ben S . Pine, M.D.* W. Peter Hansen*

Martin S . Litwin, M.D.**

Presented at Seminar on Laser Safety

at the Martin Company Orlando, Florfda

Hay 19- 20,1966

*Northeastern University, Boston, Massachusetts

***The George Washington University and Armed Forces Institute of Pathology, **aoswell Park Memorial Institute, Buffalo, New York

Washington, D.C.

School, Boston, Massachusetts ***Veterans Administration Hospital, West Roxbury, Massachusetts and Harvard Medical

Supported by contracts DA-49-193-MD-2436, DA-49-193-MD-2437, DA-49-193-MD-2680, Surgical Research Branch, U.S. Army Research and Development Command, Office of the Surgeon General, U.S.Department of the Army; and contract 1-R01-RH-00361 RAD, Division of Radiological Health, Bureau of State Services, United States Public Health Service, and i n part by contract AF-29(600)-5136, Air Force Missile Development Command, Air Force Systems Command, U.S.ALr Force

Washington National Record Center Ollice of the Army Surgeon General Record Group 112 Accession #: 75 - 13

CONTROL OF LASER HAZARDS AND MANAGEMENT OF ACCIDENTS

.

The development of p ro tec t ive devices and s a f e t y measures in the labora tory

and in t h e f i e l d a r e based on two d i f f e r e n t p r inc ip l e s . I n the labora tory , personnel

can, in p r i n c i p l e , be completely i s o l a t e d from the l a s e r system,

one s t r i v e s t o reduce t h e p robab i l i t y of acc iden ta l exposure of personnel t o the point

where economic f e a s i b i l i t y and c e r t a i n p r a c t i c a l problems a r e t h e l i m i t i n g f ac to r s .

The a l t e r n a t i v e t o not providing a phys ica l ly s a f e environment and not e s t a b l i s h i n g

r i g i d s a f e t y r u l e s is the occasion of acc idents and t h e i r concomitant medico-legal cos t s

The problems of e s t a b l i s h i n g s a f e f i e l d condi t ions reduces t o one of providing individua

pro tec t ion .

In p r a c t i c e , however,

T h i s type of p ro tec t ion is t y p i f i e d by s a f e t y c l o t h i n g and goggles.

Considerat ion of t h e mechanisms of laser i n t e r a c t i o n wi th b io log ica l systems

has led t o a t e n t a t i v e o u t l i n e of a program fo r t h e con t ro l of l a s e r hazards and

management of l a s e r acc idents . ( 1 , 2 )

A. Control of Laser Hazards

1. General Adminis t ra t ive Procedures

a . Personnel

(i) Laser Hazard Control Off icer

(ii) Deputy Laser Hazard Control Off icer

(iii) Laboratory Laser Hazard Control Off icer

b. Medical Supervis ion

C . Records

2. Laboratory Design and Operation

3. Pro tec t ion Standards and Dosimetry

B. Management of Laser Accidents

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A. Control of Laser Hazards

1. General Adminis t ra t ive Procedures

a. Personnel

(i) Laser Hazard Control Of f i ce r

The l a s e r hazard con t ro l o f f i c e r should be respons ib le fo r a l l f a c t o r s

a s soc ia t ed wi th l a s e r s a f e t y wi th in the organiza t ion .

t o the sen ior management or ch ief execut ive o f f i c e r of the organiza t ion and should

c a r r y a u t h o r i t y regarding l a s e r s a f e t y which can be countermanded only by the ch ief

execut ive o f f i c e r .

He should be respons ib le only

He should have f u l l records concerning a l l s t u d i e s us ing l a s e r s

c a r r i e d out with in the organiza t ion , a s w e l l a s information concerning personnel and

t h e c h a r a c t e r i s t i c s of t h e equipment.

equipment or assoc ia t ed experiments, a s ses s ing hazards t o t h e ex ten t f e a s i b l e and

providing safeguards.

forwarded t o him in w r i t i n g in order t h a t he be a b l e t o a s ses s p o t e n t i a l hazards

p r i o r t o t h e i r in t roduct ion .

He is respons ib le fo r monitoring l a s e r

Information regard ing proposed experiments should be

He should provide information regarding i n s t a l l a t i o n of new

systems, be present during the i n i t i a l opera t ion of a l a s e r system o r during major

modi f ica t ions of experiments in progress.

He is respons ib le f o r i n s t r u c t i n g a l l personnel a s soc ia t ed with

l a s e r s t u d i e s on the subjec t of l a s e r s a fe ty .

in t h e event of any l a s e r acc ident .

He should be a v a i l a b l e and n o t i f i e d

The Laser Hazard Control Off icer may be a medical o f f i c e r

t r a ined in l a s e r hazard c o n t r o l , or an engineer i n t e r e s t e d in general s a f e t y with

cognizance o f l a s e r hazards.

(ii) Deputy Laser Hazard Control Off icer

Since t h e Laser Hazard Control Of f i ce r may be absent or

unavai lab le , a Deputy Laser Hazard Corn-rol Off icer should be appointed t o a c t in

h i s p lace a s a s u b s t i t u t e when t h e former is not ava i l ab le .

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(iii) Laboratory Laser Hazard Control Off icer

A l l l abora tory a reas should have an ind iv idua l designated a s

a s a f e t y o f f i c e r f o r t h a t a r ea . H e is t o r e p o r t t o t h e Laser Hazard Control Off icer

i n s o f a r a s l a s e r s a f e t y is concerned He is respons ib le f o r the day-to-day s a f e t y

wi th in the labora tory and maintenance of adequate records regarding compliance

wi th s a f e t y s tandards . This is important s ince i f no records a r e kept regarding

experiments, p e r t i n e n t information r e l a t e d t o au acc ident w i l l not be ava i l ab le .

b. Medical Supervis ion

The purposes of medical superv is ion a r e t o dea l with t h e medical

and medico-legal a spec t s of l a s e r hazards. Since the long-term hazards a r e unknown,

a balance must be achieved between poss ib ly app l i cab le procedures and those which

can be considered p r a c t i c a l .

Medical supervis ion should inc lude ’an i n i t i a l medical examination.

The h i s t o r y should emphasize previous r a d i a t i o n exposures and a spec t s a s soc ia t eh

wi th the eyes and sk in . The physical examination should g ive more than usual

a t t e n t i o n t o t h e eyes and sk in , and should be accompanied by labora tory s tud ie s .

Follow-up s t u d i e s should be c a r r i e d out p e r i o d i c a l l y probably a t t h r e e month t o

one year i n t e r v a l s and following an a c t u a l or suspected acc ident .

w i l l depend on t h e equipment used, and t h e s t u d i e s being c a r r i e d out .

The t i m e i n t e r v a l

(i) Radiat ion Exposure History

A h i s t o r y should be obtained regarding previous exposure t o

l a s e r r a d i a t i o n , t o high i n t e n s i t y r a d i a t i o n in the r a d i o frequency or microwave

r eg ions , and t o u l t r a v i o l e t , x-ray, gamma r a y and nuclear r a d i a t i o n . Records

of previous r a d i a t i o n exposure should be obtained.

(ii) General Medical His tory

P a r t i c u l a r a t t e n t i o n should be paid t o a previous h i s t o r y of

i n j u r y , i n f e c t i o n , or inflammation of t h e eyas or v i s u a l d i s turbances . A t t en t ion

t o t h e skin should include information iegard ing a l l e r g y , pho tosens i t i v i ty ,

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previous s u r g i c a l exc i s ions , or abnormal wound heal ing.

(iii) Physical Examination

The physical examination should include a complete ophthalmologic

and dermatologic eva lua t ion c a r r i e d out by persons with considerable experience

in t h i s a rea . For example, the ophthalmologist m u s t have knowledge of o the r types

of r a d i a t i o n i n j u r y i n add i t ion t o knowledge r e l a t e d t o t h e e f f e c t s of l a s e r

r ad ia t ion . The eye examination should, of course , include the usua l t e s t s of

v i s u a l a c u i t y , r e f r a c t i o n , s l i t lamp examination and a c a r e f u l ophthalmoloscopic

examination under f u l l mydriasis with both white and red f r e e l i g h t .

of t h e c r i t i c a l a r eas of the macula and fovea by e i t h e r rou t ine tangent screen

examination or campimetry is too tedious and genera l ly not p r a c t i c a l . One rap id

method of sc reening t h i s important c e n t r a l a rea and one which may be c a r r i e d out

qu ick ly and simply by a technic ian or t r a ined a i d e is the use of an Amsler gr id .

A negat ive screening here adds t o t h e s t r e n g t h of a negat ive rou t ine type of

examination.

by o the r means.

Screening

These s p e c i a l t e s t s may be reserved f o r eva lua t ion of l e s i o n s de tec ted

Fundus photography is probably no t , in genera l , u se fu l a s a

r o u t i n e screening procedure unless an ophthalmoscopically de t ec t ab le l e s ion o r

o t h e r eye pathology is found. Photographic recording of t h i s l e s ion may then be

of cons iderable value. Fundus photography may, however, provide a base l ine f o r

eva lua t ion of progression of any v i s i b l e l e s ion which may develop.

a fovea l l e s i o n should be done w i t h g rea t c a r e , f o r e c l i p s e burns f requent ly

produce ophthalmoscopically de t ec t ab le l e s i o n s i n t h e foveal a r ea with no

apparent de fec t i n t h e c e n t r a l v i s u a l acu i ty .

Evaluation of

The dermatologic examination should inc lude p a r t i c u l a r a t t e n t i o n

towards t h e presence of kera toses and sk in malignancies, a s w e l l a s benign

dermatoses, p a r t i c u l a r l y those r e l a t e d t3 photosens i t iza t ion .

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These should include a complete blood count , r o u t i n e

u r ineana lys i s and blood smear for medico-legal a s wel l a s medical purposes.

c . Records

Adequate records should be kept regarding:

(i) Personnel

(ii) C h a r a c t e r i s t i c s of t h e l a s e r f a c i l i t i e s wi th in the organizat ion.

(iii) Operation of l a s e r f a c i l i t i e s

( iv ) Accidents

2. Laboratory Design and Operation

The a t t e n t i o n which should be d i r e c t e d towards labora tory design

and opera t ion is dependent on the energy, power l e v e l s and wavelengths used.

Should high energy or high power equipment be used, the operat ions area should be

separa ted from the charging bank or power supply and from the l a s e r output area.

Under these circumstances in t e r locks a r e requi red t o prevent i nd iv idua l s from

e n t e r i n g the l a s e r f i r i n g a rea or t h e capac i to r bank a r e a , during charging of

the bank or f i r i n g of t h e u n i t . Information concerning the l a s e r beam i n t e r -

a c t i o n can be obtained us ing c losed c i r c u i t t e l e v i s i o n systems or photography

of e i t h e r t h e i n t e r a c t i o n or t h e meter measurements necessary wi th in t h e beam area.

A s i g n i n d i c a t i n g t h a t the area is a l a s e r labora tory should be posted a t t h e

en t rance of t h e laboratory.

t o red can be used t o enhance s a f e t y dur ing opera t ion of the l a s e r equipment.

The dual system enhances the r e l i a b i l i t y of t h e s a f e t y system, s ince one v i s u a l

s i g n a l such as a l i g h t must be on and the o the r o f f a t a l l times.

s i g n a l , i t is not known whether t h e l a s e r is not being opera ted , or the l i g h t

has burned out . Auditory s i g n a l s , in same cases , may d e t r a c t from r a t h e r than

add t o s a f e t y , p a r t i c u l a r l y s i n c e dual 3udi:ory systems a r e imprac t ica l .

A dual set of v i s u a l s i g n a l s switching from green

With a s i n g l e

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There should be s u f f i c i e n t i s o l a t i o n between var ious l a s e r

u n i t s operated i n t h e same a r e a , t o prevent exposure of personnel t o

r a d i a t i o n from t h e o the r l a s e r a reas . Enclosure of t h e l a s e r head, t h e

i r r a d i a t i o n s i t e and t h e space between them (when f e a s i b l e ) w i l l a s s i s t i n

reduct ion of hazards.

The room should be w e l l l i g h t e d t o minimize pupi l diameter

and consequent l i g h t absorp t ion by t h e eye.

wa l l s w i t h a f i r e r e s i s t a n t ma te r i a l which w i l l absorb a t t h e l a s e r

wavelength used w i l l be of value.

l a s e r g l a s ses dur ing opera t ion s ince i n t e r a c t i o n of the beam with ma te r i a l

may r e s u l t in backscat tered r a d i a t i o n a t wavelengths o ther than those of

the inc iden t r a d i a t i o n , P which t h e a t t e n u a t i o n f a c t o r of the g lasses may

be low.

cumulative r a d i a t i o n exposure a r e unknown. Another f a c t o r which w i l l l i m i t

t h e e f f ec t iveness of g lasses is t h a t t h e r a d i a t i o n i s not s c a t t e r e d i n a

mathematically p red ic t ab le mpnner, and in some ins tances may be

s c a t t e r e d predominantly i n a s p e c i f i c d i r ec t ion . Glasses t h a t have been

d i r e c t l y exposed t o unusual ly high i n t e n s i t y r a d i a t i o n should be

discarded s i n c e t h e i r e f f ec t iveness may be degraded, without obvious

gross defec ts . For ins tance , we have observed delayed s p a l l a t i o n of

goggle f i l t e r s .

beam o r back-scat tered r a d i a t i o n r a t h e r than depending on glasses .

count-down procedure during opera t ion of t h e l a s e r should be used.

Pa in t ing o r coa t ing of t h e

F u l l r e l i a n c e should not be placed on

This is of p a r t i c u l a r s ign i f i cance s i n c e the e f f e c t s of long term

Consequently, i t is pre fe rab le t o avoid looking a t t h e

A

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A t u l t r a v i o l e t and in f r a red wavelengths, the problem is accentuated

s i n c e t h e beam is not ~ i s i b l e ! ~ )

o r t he area so arranged t h a t an ind iv idua l cannot e i t h e r pass through the d i r e c t

beam, o r be subjec t t o s c a t t e r e d r ad ia t ion .

The a rea should be monitored before and a f t e r sh i e ld ing t o determine t h e r ad ia t ion

d i s t r i b u t i o n . This problem is p a r t i c u l a r l y acu te with continuous, high power

lasers, s ince constant monitoring of the a rea by an ind iv idua l throughout the

on time of t he beam is impract ical . With semiconductor lasers, the problem of

s t rong o f f - ax i s peaks must be recognized. I n , b o t h these cases , monitoring is

requi red t o determine the r a d i a t i o n l e v e l s in a l l regions of t he room.

Consequently, e i t h e r t he beam should be enclosed

This may requ i r e the use of shielding.

Although d e f i n i t i v e information concerning hazards assoc ia ted

with the capac i tor discharge system has not been obtained, s u f f i c i e n t data have been

accumulated on e l e c t r i c a l hazards t o ind ica t e the marked dangers a r i s i n g from the

high energy system. Although in t e r locks and discharge r e s i s t o r s on the capac i tor

bank are used, i t is important t o note t h a t time cons tan ts are involved and the

discharge system may f a i l .

be used a s a backup device p r i o r t o contact with the capac i tor bank.

rods with v i s i b l e grounding should be a s soc ia t ed with each bank.

Manual discharge using a grounding rod should therefore

These grounding

In add i t ion , s p e c i a l cons idera t ion should be given t o the choice

of o r i g i n a l cab les . The cab le chosen should be spec i f i ed as corona f r e e in

add i t ion t o the adequate d i e l e c t r i c s t r e n g t h f o r the l a s e r with which i t is t o be

used.

important, t he s i n g l e most important test is t he "hi-pot'' or d i e l e c t r i c s t r eng th t e s t .

These tests can be made with r e a d i l y a v a i l a b l e t e s t i n g apparatus o r by the cable

Although a c t u a l observat ion of the cab le and con t inu i ty tests a r e very

manufacturers t e s t i n g f a c i l i t y . The d i e l e c t r i c tests w i l l g ive an ind ica t ion of the

present s t r eng th of t h e i n su la t ion and L i w corona test w i l l i nd ica t e the presence

of corona. I f p resent , t h i s corona C ~ U S P J ozone, which is highly co r ros ive t o some

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d i e l e c t r i c s and may cause u l t ima te f a i l u r e of t h e cable .

a c a b l e t h a t shows t h e presence of corona should be replaced.

To be on t h e s a f e s i d e ,

The cables from the power supply t o t h e laser head should be

placed so that acc iden ta l contac t with them cannot occur , s i n c e these cables c a r r y

high cu r ren t a t high vol tage . Equipment such as osc i l loscopes should be 80 placed

t h a t the observer is not requi red m t u r n or face towards the beam during charging

of the bank and f i r i n g of the l a se r .

osc i l loscopes a s soc ia t ed w i t h the laser equipment and wi th t h e experiments, should

be 80 arranged and pro tec ted as t o present minimal hazards t o t h e inves t iga to r s .

Meters which measure high vo l t ages , and

The placement of firing buttons must be a t a d i s t ance from those

of t h e charge or hold but tons in order t o prevent acc iden ta l discharge of t h e

l a s e r through p res s ing of the wrong button. Unless automatic recharge of t h e

capac i to r bank is requi red f o r experimental purposes, charging should be under

manual c o n t r o l , and not automatic.

Capaci tor discharge through o ther than t h e usua l discharge

c i r c u i t inc luding d ischarge due t o capac i to r breakdown may occur.

a s soc ia t ed wi th t h i s can be minimized by t h e use of d i s t ance and mechanical

s h i e l d i n g between t h e opera tor and t h e bank.

breakdown may be accompanied by a loud sound.

the bank and by sound damping techniques.

Hazards

Discharge of a bank due t o capac i to r

This can be minimized by s e c t i o n a l i z i n g

There are t h r e e poss ib l e approaches t o t h e problem of in t e r locks :

(i)

(ii)

(iii)

No i n t e r l o c k s on t h e equipment.

In t e r locks which do not have a manual ove r r ide as p a r t of t h e i r design.

In t e r locks which a r e au tomat ica l ly reset on c losu re of cab ine t s

or equivalent equipment fol lowing disablement f o r r e p a i r s -- t h a t is,*

i n t e r l o c k s with a b u i l t - i n manual over r ide .

No i n t e r l o c k s on t h e e.uipment is probably undesirable . However,

i t must be conceded t h a t under these circumstances t h e r e w i l l be no r e l i a n c e placed

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on s a f e t y f ea tu res which may malfunction and the bank i s always considered dangerous.

In t e r locks which do not have a manual over r ide must be cheated o r

jumped t o a l low f o r s e rv i c ing , I f the jumper is not removed, t h i s r e s u l t s i n an

undesirably hazardous condi t ion. An i n t e r l o c k with a b u i l t - i n manual over r ide

which au tomat ica l ly resets on c losu re is the type of i n t e r l o c k which should be

incorporated i n a l l laser systems.

t h e equipment with t h e door unlocked, or permits experiments t o be c a r r i e d o u t ,

where necessary.

It permits the s e r v i c e personnel t o t roubleshoot

Sa fe ty r egu la t ions a s soc ia t ed with laser systems a r e dependent

upon t h e type of laser system which is t o be used, and the environment i n which it

l a t o be located.

f a c t o r s , inc luding waveiength, continuous o r pulsed opera t ion , energy and power

a v a i l a b l e from t h e l a s e r , and atmospheric condi t ions. With pulsed, s i n g l e shot

systems, t h e u n i t i s e s s e n t i a l l y s a f e except when charged unless t h e r e is a charge

l e f t on t h e c a p a c i t o r bank.

system must be i n s t r u c t e d t o charge the capac i to r bank (or equivalent system) only

when t h e laser is t o be used, t o f i r e i t immediately, or t o discharge t h e capac i tor

bank immediately and completely.

t a sks during charging and f i r i n g of t h e laser.

c a r r y on d iscuss ions with o the r i nd iv idua l s or engage in s i m i l a r t a sks during

charging and f i r i n g the laser.

The degree of precaut ion necessary w i l l depend on a number of

The ind iv idua l s a s soc ia t ed with t h e pulsed l a s e r

Under no circumstances must they undertake o ther

They must not answer telephones,

Since the hazard wi th pulsed lasers is present only during t h e

per iod of bank charging and l a s e r f i r i n g , the type of hazard f o r pulsed, s i n g l e

s h o t opera t ion is similar fo r l a s e r s a t a l l wavelengths in t h e u l t r a v i o l e t , v i s i b l e

and in f r a red .

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High p.r . f . and continuous l a s e r s possess comon problems s ince

they may opera te f o r a cons iderable per iod of t i m e without s u f f i c i e n t a t t e n t i o n being

d i r e c t e d towards prevent ion of ind iv idua ls from en te r ing t h e a rea and t o the loca t ion

of i nd iv idua l s w i th in t h a t area.

opera t ing i n t h e u l t r a v i o l e t and i n f r a r e d por t ions of the spectrum where the

r a d i a t i o n i s not v i s i b l e . Under these circumstances, t h e l a s e r a r ea mst be

considered a s hazardous a t a l l t imes, i n a manner similar t o t h a t of an a rea

conta in ing r ad ioac t iv i ty .

a second set of b a r r i e r s can be used t h a t a r e s i m i l a r t o those fo r r ad ioac t ive

or high vol tage a reas .

equiva len t , i n conjunct ion with appropr ia te s igns a t t h e same d is tance . These

w i l l a c t as a second precaut ionary b a t r i e r , thus l i m i t i n g acc iden ta l exposure.

A monitoring approach s i m i l a r t o t h a t used fo r r a d i o a c t i v i t y can be employed fo r

continuous, o r high p . r . f . l a s e r s , p a r t i c u l a r l y f o r those ope ra t ing i n t h e non-

v i s i b l e po r t ion of t h e spectrum.

s e n s i t i v e a rea d e t e c t o r s , app ropr i a t e ly loca ted a t t h e b a r r i e r region and hand

he ld survey d e t e c t o r s which can be used t o monitor and measure t h e r a d i a t i o n

present w i th in an area.

t h e wavelength band of i n t e r e s t and should be capable of d i scr imina t ing aga ins t t h e

background r a d i a t i o n present .

This problem is p a r t i c u l a r l y acu te with l a s e r s

As w e l l a s t h e usual room en t ry i n t e r l o c k techniques,

This b a r r i e r can c o n s i s t of a white tape b a r r i e r or i t s

This approach can cons i s t of s u f f i c i e n t l y

The de tec to r s should have t h e requi red s e n s i t i v i t y over

For C 0 2 l a s e r s , thermofax paper i s d isco lored brown a t energy

2 d e n s i t i e s of t h e order of 1 joule/cm . Thermocouples w i l l r e a d i l y de t ec t

m i l l i w a t d c m 2 , and thermopiles microwatts/cm 2 . Pro tec t ive face s h i e l d s should be loca ted ou t s ide t h e entrance t o -

these a r e a s , p a r t i c u l a r l y where continuous or high p.r . f . u n i t s are used i n the

u l t r a v i o l e t or i n f r a r e d region.

a l l personnel w i th in t h e area and shone'd be re turned t o t h e s h i e l d rack upon leaving.

These m o t e c t i v e face s h i e l d s should be worn by

Washington National Record Center Ofice of the Army Surgeon General Record Group 112 Accession #: 75 - 1'3

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Considerat ion can be given t o co lo r coding and s igns a t en t rance a reas t o

i n d i c a t e the c l a s s of l a s e r being used, i n order t h a t i nd iv idua l s genera l ly a s soc ia t ed w i t h

these systems, but not d i r e c t i o n r e l a t e d t o the s p e c i f i c p ro jec t be aware of the types of

u n i t s being used.

With high power continuous l a s e r s , such as t h e CO2 l a s e r s , f i r e r e s i s t a n t

ma te r i a l is mandatory.

and f l e x i b l y providing sh ie ld ing of the wa l l s i n an area which is not completely f i reproof .

The use of s e v e r a l asbes tos shee t s w i l l permit the top shee t t o be replaced a f t e r i t has

burned through, before t h e underlying shee t is damaged, thus l i m i t i n g the f i r e hazard.

The presence of f l a m a b l e ma te r i a l must also be r e s t r i c t e d .

Asbestos shee t o r c l o t h has been found t o be s u i t a b l e f o r r ap id ly

Figure 1 shows a focused C 0 2 l a s e r beam i g n i t i n g c lo th . The ign i t ed c l o t h

cont inues t o burn.

o r i t s equiva len t which can be r ap id ly unfastened.

i E t h a t should i t ca t ch f i r e , one can remove t h e coat . On the o the r hand, s tandard

s t r e e t c l o t h i n g is d i f f i c u l t t o remove quickly.

f i r e hazard from these i n f l a m a b l e ma te r i a l s , if present , must be ava i l ab le .

This br ings up the quest ion of whether one should wear a l ab coat

The advantage i n wearing a l ab coa t

F i r e ex t inguishers capable of combating

Figure 2 shows a n acc iden ta l burn of a hand for ty- two hours post

i r r a d i a t i o n wi th a C02 l a s e r .

from high vo l t age equipment i n the immediate v i c i n i t y on pu l l ing the hand away.

cau t ion must be exerc ised , i n t h i s r e spec t , when s e t t i n g up equipment.

I n acc idents of t h i s type, severe i n j u r y could r e s u l t

Extreme

Windows should be covered t o prevent t ransmission of l a s e r r a d i a t i o n

a t v i s i b l e wavelengths through the window.

cons iderable care must be taken with windows i n the a r e a , s i n c e the windows may be

opened wi th r e s u l t a n t paasage of t h e beam through the open window. The problem of

r e f l e c t i o n of r a d i a t i o n from windows must a l s o be guarded aga ins t .

With u l t r a v i o l e t and in f r a red l a s e r s ,

Labora tor ies should be w e l l v e n t i l a t e d , s ince i n s u f f i c i e n t v e n t i l a t i o n

may l ead t o t h e accumulation of noxious gases, p a r t i c u l a r l y when these a r e being

used i n a continuous flow gas l a s e r . Although t h i s problem is minimized

i n a sea l ed system, i t is not e l i m i n a t e < , PS the system m y crack, w i t h r e l e a s e of

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t h e enclosed vapors.

mercury, carbon monoxide and hydrogen cyanide.

o ther materials u t i l i z e d i n experimental systems should be inves t iga t ed , usua l ly

by a l i terature search , previous t o t h e i r study a s a l a s e r medium.

Examples of these gases include ch lor ine , bromine, lead,

The toxicology of t he gases and

A second reason f o r adequate v e n t i l a t i o n is r e l a t e d t o the l i qu ids

and gases used t o purge and cool l a s e r s .

have been used fo r cool ing lasers, including s o l i d s t a t e and semiconductor un i t s .

This may r e s u l t i n the formation of l i q u i d oxygen which can combine with d i r t and

grease t o form an explosive hazard. Styrofoam and s imi l a r ma te r i a l s should not be

used in l i q u i d n i t rogen o r l i q u i d helium t r a n s f e r l i n e s because of the poss ib le

explosive hazard a s soc ia t ed with production of l i q u i d oxygen,

Both l i q u i d n i t rogen and l i q u i d helium

I n conjunction with the use of cryogenic l i q u i d s , i t is important

t h a t adequate r e l i e f va lves be present in the system, t o prevent buildup of pressure

on b o i l o f f . It is a l s o e s s e n t i a l t h a t procedures be adopted which w i l l prevent

an explosive o r inflammable gas mixture from being connected t o a l a s e r system i n

l i e u of t he des i red gas mixture. In order t o minimize the hazard due t o the above,

or due t o trace contamination of tanks, i t is des i r ab le t o operate the laser system

seve ra l times a t low vol tage l e v e l s , following connection of a new tank t o the system.

Good v e n t i l a t i o n w i l l a l s o minimize the s c a t t e r i n g hazards

a s soc ia t ed with dus t or smoke present i n the atmosphere.

Other f ac to r s include the usua l ones of r e s p o n s i b i l i t y and

a u t h o r i t y being vested i n one ind iv idua l (Laboratpry Laser Hazard Control Off icer )

i n so fa r a s making c e r t a i n t h a t the a rea is secure p r io r t o operat ion of t he u n i t .

He should be respons ib le f o r charging the bank and f i r i n g the u n i t . Working in

p a i r s is important. The s a f e t y procedures, precaut ions t o be taken, techniques

f o r mouth-to-mouth r e s u s c i t a t i o n , t he n m e s , addresses and telephone number of the

physician, Laser Hazard Control O f f i c e , , and t h e ophthalmologist should be posted.

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3. Pro tec t ion Standards and Dosimetry

Due t o the incompleteness of our knowledge concerning b io log ica l

e f f e c t s , p a r t i c u l a r l y with regard t o long-term e f f t c t s , i t is not poss ib le t o s e t

f i rm standards a t t h i s time. A u s e f u l gu ide l ine f o r pro tec t ion insofar as i m e d i a t e

or sho r t term e f f e c t s i s concerned, i s t h e minimal threshold dose of r a d i a t i o n

requi red t o produce in jury .

Considerable a t t e n t i o n has been d i r ec t ed towards determination

of threshold doses of pulsed lastr r a d i a t i o n fo r damage t o the eye, p a r t i c u l a r l y

with respec t t o i n j u r y t o the re t ina-choro ida l layers . Biological v a r i a b i l i t y ,

including heterogenei ty , pigmentation and blood supply and ex t rapola t ion of s tud ie s

on animals t o man are f a c t o r s which must be considered. The threshold value

obtained w i l l be dependent on t he method used.

examination and photography, microscopic s t u d i e s , histochemical and enzymatic

techniques, e l e c t r o n microscopic investigation and the measurement of e l e c t r i c a l

changes by electroret inography.

have been c a r r i e d out by William T. Ham, Jr., Walter Geeraets, Ben S. Fine, and

Milton Zaret, E. &. In general , t h e threshold dose a t 6943 g, non-Q-switched,

mil l isecond exposure, f o r damage t o t h e r e t i n a is in t he range of 0.5 t o 1 j o u l e

per cm2

appears t o decrease with decreasing pulse durat ion.

I n our s t u d i e s , the threshold dose f o r gross v i s i b l e damage t o

Such methods include ophthalmoscopic

Studies on t he eyes t o determine threshold e f f e c t s

inc ident a t the r e t i n a . The energy required t o produce threshold l e s ions

the sk in of m i c e appears t o be of the same order of magnitude a s that f o r the eye.

The h i s to logy may d i f f e r due t o r e f l e c t i v i t y , s c a t t e r and diathermanous proper t ies

of t he skin of mice, as w e l l as b io log ica l fac tors .

was obtained a t high peak power l e v e l s with Q-switched systems as compared t o

thresholds a t longer pulse durat ions.

A lower sk in threshold dose

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These da ta in conjunct ion with a s a f e t y f a c t o r of a t least

100 provide guide l ines f o r r a d i a t i o n p ro tec t ion s tandards a t t h e ruby wavelength.

Order of magnitude c a l c u l a t i o n s i n d i c a t e t h a t d i r e c t viewing 0

of even a 1 mi l l iwa t t gas l a s e r a t 6328 A is extremely hazardous.

considerable c a r e should be taken in adjustment of even low power gas l a s e r s .

Standards with r e spec t t o high vol tage e l e c t r i c a l equipment

Consequently,

should comply with acceptab le s tandards of e l e c t r i c a l engineer ing inc luding those

of the A. S. T. M., A.S.A., and I . E . E . E . and a r e re ferenced i n E l e c t r i c a l

Engineering Handbooks. The s p e c i f i c a t i o n s set by t h e appropr ia te agencies must

be complied with f o r the systems t o be used i n t h e f i e l d .

It is necessary t h a t t h e equipment designed or purchased by a

company comply with uniform standards adopted by t h a t company.

i n t e r l o c k s a s soc ia t ed with a l l l a s e r equipment should be of one type, grounding

rods should be incorporated in the equipment, and grounding techniques f o r

cab ine t s be c o n s i s t e n t and s a t i s f a c t o r y .

be kept informed of a l l purchases proposed or pending in order t h a t some of the

above requirements be incorporated i n t o t h e spec i f i ca t ions .

For example,

The Laser Hazard Control Of f i ce r should

Dosimetry of two types is des i r ab le . One, incorpora t ing a

photodetec tor , would measure instantaneous r a d i a t i o n i n t e n s i t y , f o r p ro tec t ive

purposes; t h e o the r would measure cumulative exposure f o r medico-legal, a s w e l l a s

medical purposes.

X and gamma rad ia t ion .

because of the s h o r t pu lse durat ion.

g l a s ses may provide some pro tec t ion .

provide information regarding r a d i a t i o n i n t e n s i t y a t a poin t , f o r succeeding pulses ,

o r f o r cont inuously ope ra t ing u n i t s .

a s soc ia t ed wi th t h e l a t t e r type of dos-.meter, i t o f f e r s a mean8 f o r maintaining

exposure below maximum permiss ib le dose I~vals.

These two types of dosimetry a r e used f o r personnel exposed t o

Dosimetry p ro tec t ion fo r a s i n g l e pulse is not f e a s i b l e

Fur ther development of adapt ive f i l t e r

The former type of dosimeter can, however,

nl.rhough t h e r e are a number of problems

Washington National Record Center OiXce of the Army Surgeon General Record Group 112 Accession #: 75-13

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Although s o f t x-rays have been produced a t t h e foca l region of

a q-switched l a s e r pu lse , t h e x-ray energy and i n t e n s i t y is low.

systems opera te a t r e l a t i v e l y low vol tage (< 5kv) with l i t t l e a s soc ia t ed x-ray

hazard.

hard t u b e modulator or equiva len t system assoc ia t ed with it.

x-rays.

type should be inves t iga t ed , and precaut ionary measures i n s t i t u t e d . These can be

minimized by t h e usua l t h r e e f a c t o r s ~ sh ie ld ing , d i s t ance and t i m e .

important t o note t h a t f i l m badge u n i t s and o the r types of x-ray de tec to r s a r e

responsive only over a range of wavelengths. The appropr i a t e de t ec to r must be

s e l e c t e d t o cover t h e range of i n t e r e s t .

Most l a s e r

However, t h e n i t rogen l a s e r ope ra t ing a t vo l t ages i n excess of 2Okv has a

This may resul t in

The source, q u a l i t y and i n t e n s i t y d x-rays a s soc ia t ed wi th systems of t h i s

It is

B. Management of Accidents

F i r s t a i d should be r e s t r i c t e d t o minimal, e s s e n t i a l

manipulation of t h e p a t i e n t as requi red for a r r e s t of hemorrhage, coverage of the

a f f e c t e d reg ion w i t h s t e r i l e gauze, and inmobil izat ion of t h e a f f e c t e d reg ion ,

p a r t i c u l a r l y in t h e event of f r a c t u r e following e l e c t r i c shock, In t h e case of

r e s p i r a t o r y arrest , mouth-to-mouth a r t i f i c i a l r e s p i r a t i o n should be i m e d i a t e l y

begun and continued u n t i l medical a t t e n t i o n is obtained.

and knowledge necessary t o apply con t ro l l ed countershock in t h e sho r t per iod

a v a i l a b l e if v e n t r i c u l a r f i b r i l l a t i o n occurs and t o at tempt pacemaking is not

a v a i l a b l e in t h e f i e l d . Considerat ion can be given t o maintenance of card iac

output by ex te rna l message.

a t t e n t i o n .

a l s o on c a l l a t a l l t imes, should be a v a i l a b l e for acc idents involving regions

o the r than t h e eye.

The equipment, techniques

A l l acc idents should r ece ive i m e d i a t e medical

An ophthalmologist should be on c a l l a t a l l times. A general physician,

Their phone numbers should be posted i n t h e laboratory.

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Since s p e c i f i c treatment of t he laser induced in ju ry i s not

a v a i l a b l e , medical management of t h e immediate in ju ry w i l l follow the usual

procedures f o r t he treatment of t raumatic l e s ions of comparable degrees of sever i ty .

Ret ina l damage, as previously mentioned, is i r r e v e r s i b l e and

medical c a r e c o n s i s t s mainly in eva lua t ion of t he damage and prevention of poss ib le

complications. Surface burns due t o u l t r a v i o l e t l i g h t a r e genera l ly simply cared

fo r with t o p i c a l medlcatlons but a severe ir i t is or i r r i d o c y c l i t i s r e s u l t i n g from

impact of s t rong r a d i a t i o n on the ir is may r equ i r e the use of cycloplegics and

perhaps even systematic s t e r o i d s t o con t ro l t he i n f l a m t i o n .

For those l a s e r s operat ing on e i t h e r s i d e of t he v i s i b l e spectrum,

cornea l damage becomes a considerable problem; i n the near u l t r a - v i o l e t only

s u p e r f i c i a l burns t r e a t e d i n the usual manner of anee the t ics and a n t i b i o t i c s may be

s u f f i c i e n t . I n t h e i n f r a r e d and f a r i n f r a red , damage may be very marked producing

not only a kera toconJunct iv i t ies but severe k e r a t i t i s leading even t o a dense

cornea l scar.

wi th t o p i c a l and systemic s t e r o i d s a s well as cyclopegic drugs such as a t rpp ine

and h m t r p p i n e . This l a t t e r form of damage t o the cornea, and perhaps i r i s end

l ans , may occur wi th the new CO2

(Pig.3,4).

by t h e pigment epi thel ium of the ir is i n contac t with the lens i s a d i s t i n c t

p o s s i b i l i t y when whole white l i g h t i s used or perhaps with carbon dioxide lasers .

This damage i s t h e o r e t i c a l l y and perhaps, backed by some experiments, more ser ious

t o the lens where the ir is does not provide a hea t sh i e ld .

l ens is more pro tec ted by the f a c t t h a t i t i s not i n contac t with the p i b e n t

epi thel ium of the iris which provides a heat shi2ld.

This is o f t en accompanied by an i r i t is , both of which can be t r e a t e d

l a s e r s t h a t are coming i n t o widespread use

Catarac t production due t o a rise i n l o c a l teapera ture by absorpt ion

The periphery of the

The problem of CO2 h se r damage t o the eye i s accentuated by

the f a c t t h a t lasers of t h i s type arr easy t o bui ld and make operat ional . Since

Washington National Record Center Ollice o f the Army Surgeon General Record Group 112 Accession #: 75 - I3

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r e l a t i v e l y l i t t l e s o p h i s t i c a t i o n is requi red t o cons t ruc t a C02 laser opera t ing

a t power l e v e l s from 5 t o 20 watts, one can expect a g rea t number of remarkedly

hazardous u n i t s t o be ope ra t iona l in t h e near fu ture .

l a s e r b u i l t i n our labora tory from r e a d i l y obta inable ma te r i a l s in t h r e e weeks.

Figure 2 shows a 2 2 watt co2

F o l l o w p should be c a r r i e d out wi th p a r t i c u l a r a t t e n t i o n t o

delayed anatomical and func t iona l dis turbances of t h e eye and t o t h e poss ib l e

l a t e mani fes ta t ions of chronic inf la tmatory changes in t h e sk in and deeper

s t r u c t u r e s .

The delayed e f f e c t s in t h e sk in and subcutaneous t i s s u e s may

include s c a r r i n g , a t rophy, indolen t u l c e r s , p e r s i s t i n g s inuses , chronic granuloma

and poss ib ly malignant transformations. Treatment of these l a t e sequelae should

be in accordance with e s t ab l i shed dermatological methods of management.

Accidents involving p a r t i c u l a r l y s e n s i t i v e si tes, such a s j o i n t s ,

cranium, s u p e r f i c i a l l y loca ted blood v e s s e l s and nerves , r equ i r e the inmediate

a t t e n t i o n of t h e r e spec t ive medical s p e c i a l i s t s .

t h a t trauma t o these reg ions cannot be assessed on t h e b a s i s of t h e ex ten t of the

s u p e r f i c i a l i n ju ry ; t h e p a t i e n t should consequently be c a r e f u l l y followed in t h e

event of i n j u r y t o these regions.

Experimental f ind ings i n d i c a t e

Each acc ident should be repor ted t o the Laser Hazard Control

Officer as w e l l a s t o t h e a t t end ing physician.

should be made a v a i l a b l e t o the Laser Hazard Control Off icer .

Abs t rac ts of t h e medical records

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Energy t ransformations assoc ia ted with the i n t e r a c t i o n of l a s e r r a d i a t i o n

w i t h b io logica l systems a r e of s igni f icance .

and power l e v e l s and wavelengths) d i r ec t ed towards e luc ida t ion of the mechanisms

of energy t ransformation is required. The r e l a t i v e s ign i f i cance of these energy

t ransformations in so fa r a s sho r t and long term b io log ica l e f f e c t s a r e concerned

i s dependent on t h e parameters of t he r a d i a t i o n and the p rope r t i e s of t h e

b io log ica l system.

than those due t o the r a d i a t i o n , per s e , have been considered.

have been presented regarding c o n t r o l d hazards and management of accidents .

Further i nves t iga t ions on the b io log ica l e f f e c t s of laser r a d i a t i o n w i l l r e s u l t

i n a b e t t e r understanding of t he sho r t and long term hazards, and provide a bas i s

f o r more d e f i n i t i v e recommendations regarding hazard con t ro l and acc ident management.

Fur ther s tudy (at various energy

Hazards assoc ia ted with the operat ion of l a s e r systems o the r

Some recommendations

REFERENCES

1. Fine, S . , Klein, E., Fine, B.S., Litwin, M., Nowak, W,B., Hansen, W.P., Caron, J., Forman, J . , "Mechanisms and Control of Laser Hazards and Management of Accidents," Technology), Apr i l , 1965.

Daniels, R.G., and Goldstein, B., "Lasers and Masers - Health Hazards and t h e i r Control," Federat ion Proceedings, Supplement 14, January-February.1965.

Second Conference on Laser Technology(Il1inois I n s t i t u t e of

2.

3. F ine , S . , Klein, E., Litwin, M., Peacock,G., Hamar, M. Hansen,W.P., "Biological E f fec t s of High Power Continuous N 2 - CO2 Laser Radiation a t 10.6 Microns", Federat ion Proceedings, Vol. 25, No. 2 , Par t I , March-April,1966.

Washington National Record Center OTfice of the Army Surgeon General Record Group 112 Accession #: 75-13 B o x # 3 File: I304-14 G Q ~ , S c ~ u d Mb 243b

Fig. 1, Rapid military cloth 10.6 microns. approximately :

ignition of str on irradiation Incident power io uattsjcm2.

indard at density ,

Fig. 3. Corneal lesion in a rabbit eye approximately one hour after exposure to radiation from a C02 laser: 5 watts for one second (25 joules/cm2). Most of the lesion is white, and charring of tissue is barely noticeable in the center. Neg. 66-2616-6.

AFIP

Washington National Record Center OlIice of the Army Surgeon General Record Group 112 Accession #: 75-13 Box#: 3 File: 1304 -14 6 n ~ J 5krrl~cd M b 243b

if Pig. 4. Corneal l e s i o n one hour a f t e r exposure t o r a d i a t i o n from a CO l a s e r : u l ce ra t ed bed b u t a narrow band of opaque white cornea can still be seen around the periphery of the les ion. chamber. W I P Neg. 66-2616-4.

9 watts f o r m o n e second (45 joulcs/cm2). Charred tissue cover8 most of t e

C l i n i c a l l y , t h i s l e s i o n almost pene t ra ted i n t o t h e anterior

Fig. 5 . Twenty w a t t C02 l a s e r designed and cons t ruc ted a t Northeastern Universi ty . four meters$ 0.9 cm bore diameter; Brhwster angle N a C l windows; mirror conffgura t lon var iab le- -p lane p a r a l l e l ond hcmiapherical; ex t e rna l beam coupl ing with uncoated NaCl r e f l e c t o r ; 60 cyc le exc i t a t ion ; and o v e r a l l e f f i c i e n c y , Pout/ P l i n c - 6%.

Spec i f i ca t ions as follows: a c t i v e c a v i t y length v a r i a b l e from two to

Washington National Record Center Ofice of the Army Surgeon General Record Group 112 Accession #: 75 - 13 B o x # 3 File: I304 -14 ~cccrlcce.4 bA0 2436

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