-r

Indian Journal of Pure & Appli ed Phys ics Yol. 7,7. Octoher 1999. pp. 7R7-79()

Study of radon and its progeny concentrations in an oil refinery and foundry environment

A J Khan

Department of Phys i c~. Al igarh Muslim University. Aligarh 202 002

and

A K Singh & Rajendra Prasad

Dep.l rtment o f Applied Phys ics. Z H Co llege or Engineering & Technology. A ligarh Muslim Uni versity. A li g,lrh 20200]

Received () May I 99l): rev ised 24 August 1999: accepted R September 19l)l)

LR- I 15 type II detectors wel'e used to me,lsure the radon concentrations in the dwellings or an oil rdinery anci ill some

roundri es . T he radon levels inside an oil rerinery and roundri es arc round tn be below the USEPA's remed ial action leve ls or

150 Bq m-' . The radoll concentrations in oil rerinery were round to be higher in both outdoor and indoor environment. as

compared to those round in normal background dwellings. The radon levels inside the foundri es investigated arc or the same

order as measured in dwellings or the sa ille city. The reported higher lung cancer rates in roundries may not he attri buted to

r'lcion.

I Introduction

The ri sk of lung cancer from radon decay products ex posure depends directl y on the total cumul ati ve expo­sure. Thi s is de fined as the annual average exposure times years of ex posure. Howe ver, in several cases control and ecological studies on the relation between domesti c radon ex posure and lung cancer have shown conflicting res ults t., . In consequence of this , the lung cancer ri sk of radon ex posure for t he general population is not actuall y known.

Sin ce the last IS yea rs useful studi es for radon levels in Indi an dwe llings are being conducted in our labora­tory. The results of the studies have already been pub­li s h ed~ ·h In this paper, it is proposed to measure the radon and it s progeny leve ls in the dwellings of the oi l refinery ;trea at Mathura (UP) and of some foundri es (loc k factories) in Ali garh (UP).

The Mathura Oil Re fin ery founded in 1978 has a ca pacit y of 6 MMTA and produces the followin g prod­ucts7

HSD Over 2 MMTA

Naphtha 8. 09, ()OO T A

Kerosene 6, .'i 8. ()()() T A

Petro l ~, SO. ()O() T A

LPG I, 80, (lOO T A

The petroleum refinery is supplied with crude oil from the oil fields and it sends out some or all of the wide-ranges of petroleum products to the market. Today petroleum is the source of hundreds of products ranging from gases, volatile liquids to bitumen and solid waxes. It is al so the source of the hydrocarbon feed stock to the petrochemical indust ry.

In nature, the sources of oil and gas are sedimentary rocks, namely sands, sandstone. grills , limestones and dolomites. There are occasional cases of igneous and metamorphic rocks serving as the source of petroleum . The sed imentary and igneous rocks al so contain trace amounts of D XU in varyi ng quantiti es~ which is the source of m Rn (radon). With the oil ex pl orati on. 2 \ ~ U may also be extracted. wh ich is present in crude oil and natural gas. The mean rad on activ ity concentrat ion in natural gas from the di stribution line in South Poland ') was found to be 235 Bq m-' with a maximum of 36 1 8q m- \ and a minimum of 124 Bq m-3 Refinin g of crude oi l and production of different types of petroleum prod­ucts. require several processes, such as distillati on. cata­lytic reformin g and thermal cracking, etc . which may be responsible for releasing the environmental pollutant s. Hydrogen sulphide (H2S) ex posure is considered to be one of the major pollutants in the petrol eum refinery environment. Besides hydroge n sulphide, some other pollutants are also present in the oil refinery enviro n-

7XX INDIAN J PURE APPL PHYS, VOL 37, OCTOBER 1 999

ment. Qur interest is to study the levels of radioactive pol lutant radon and i ts progeny, and their impact on the public residing in this area, with special reference to lung caner. For a comparison epidemiological studies l () in two petroleum industries of UK show the l ung cancer Standardized Morbidity Ratios (SMR's) of 0.78 and 0.80.

The radon and i ts progeny concentrations were also investigated in some foundries of Al igarh, the city fa­mous for its lOCK industry in India and abroad . The need for this study is being felt as the I nternational Agency for Cancer Research 1 1 concluded in 1 987 that i ron and stee l foundry work is carcinogenic to humans . Foundry workers are eXl'0sed to many substances, but it i s sti l l unknown which exposures in the work environment are responsible for increased lung cancer risk among foun­dry workers. However, there is no report avai lable so far on increased cancer risk vi s-a-vis petroleum and foundry operations in India.

2 Experimental Methods · Radon and its progeny concentrations were measured

in I I dwel l ings of oi l refinery premises at Mathura and I (l lock factories of Al igarh city. Some outdoor meas­urements of radon concentrations in both the places were also perfonnfd to compare the indoor and outdoor radon levels . Radon and its progeny were measured using LR- I I S type I I detectors in bare mode. The detector

piece of 2 cm x 2 cm mounted on a thick flat card was fixed on the wal l , such that it viewed a hemisphere of air

ofradius at least 6.9 cm, the range of 2 1 4po a-particle in air. No surface shou ld be closer than this range as

progeny plate-out would act as an indeterminate a-par­ticle source. The track density of a bare detector wi l l , therefore, be a function of radon progeny concentration in air. The detectors were exposed for a period of three months between February, 1 998 to May, 1 998 for each measurement. In dwel l ings of oi l refinery, the detectors were placed in drawing rooms, bedrooms, and kitchens, respectively . The dwe l l ings are situated in the refinery premises within one ki lometer radius from the refinery stacks .

After the exposure, al l tl� detectors were col lected from different places, brought back to the laboratory and etched in a constant temperature water bath under opti­mum etching condit ions obtai ned by earl ier experiments in the laboratory. The tracks registered in the detectors revealed by chemical etching process were counted by optical binocu lar research microscope with a magn ifi-

cation of 400 x. About 30(l-400 tracks from each detec­tor were counted to minimize the stat i stical error in counting of the tracks.

The uncertainty of the measured radon concentration in Bqm-3 has been estimated . The measured number of tracks in each fi lm is presumed to be Poisson d istributed and a statistical uncertainty may be estimated . In addi­tion, depending on the chemical processing of the fi lm and on the counting technique, uncertainties have been found from tests in the laboratory in the range of 1 0-I S%. Uncertainties due to detector exposllre, electro­static effects and manufacturing defects are also taken into account as stat istical error. The total uncertainty of the measured radon concentrat ion of an individual de­tector is estimated by taking the square root of the sum of the squared uncertainties.

To calculate the radon daughters concentrations in working level (WL) from the track density (tracks/cm2) observed in the detectors, these were cal i brated at Bhabha Atomic Research Center, Mumbai . The detai ls of the cal ibration experiment are given el sewhere(' . The average measured cal i brat ion factor was found to be 442 ± 60 tracks cm-2. d- I per WL. The radon concentration was estimated using the equ i l ibrium factor of (l.4S . 3 Results and Discussions

The results of the measurements of radon and its progeny concentrations in the dwel l ings of an oil refi n­ery situated at Mathura are reported in Tables 1 -3, which

SNn

2

3

4

5

6

7

8

1 0

Average

S . D .

Table I - Radon levels i nside bedrooms

Potential Radon cOile. Effective Alpha Energy ( Bq m-3) Dust:

conc. (mSv Yr· l ) (mWL)

9. 1 7 5 :l .R

9.9 R I 4. 1

1 1 .6 95 4Jl

1 1 .0 9 1 4.6

1 0. 1 83 4.2

1 0 5 86 4.3

1 25 1 02 5 . 1

1 1 .6 96 4.8

1 2 .8 1 06 5 .3

1 7 . 5 1 44 7 .2

1 1 . 7 9 6 4 . 8

2 .3 1 9 0.9

.,.. I

)...-....

.,.

.-

--<

KHAN et at.: RADON IN ENVIRONMENT 7RlJ

Tahle 2 - Radon levels inside drawing rooms

SNo Potential Radon eonc. Effective A lpha Energy ( Bq m-') Dose conc. (mSv Yr- ' ) (mWL)

1 2 .5 1 03 5 .2

2 9.9 8 1 4. 1 :I 1 2.3 1 0 1 5 . 1 4 !U 68 3.4

5 R.2 67 3.4

6 1 1.: 1 9:1 4.7

7 17 . 1 1 4 1 7 .0

X 1 6.2 1 33 6.7

l) 9.7 80 4.0

1 0 5.8 48 2.4

I I 7 . 7 63 3 .2

Average I O.X 89 4.5

S .D. 3.5 29 1 .5

Tahle :I - Radon levels inside kitchens

S No Potential Radon conc. Effective A lpha Energy ( Bq n/I) Dose conc. (mSv Yr· ' ) (mWL)

1 1.: 1 93 4.7

2 1 3 .9 1 1 4 5 . 7

3 1 4.6 1 20 6.0

4 1 0.5 86 4.3

5 1 2.:1 1 0 1 5 . 1

(, 1 6 .0 1 32 6 .6

7 1 8 .8 1 5 5 7 .8

8 1 3 .9 1 1 4 5.7

9 7 . 2 59 3.0

1 0 1 5 .8 1 30 6.5

I I 20.4 1 67 8.4

A verage 1 4 . 1 1 1 5 5 .8

S D 3 . 7 3 1 1 . 5

presents the resu l ts of radon level s in bedrooms, drawing rooms and k i tchens i ns ide the dwel l ings, respectively . The potent ial a lpha energy concentrations (PAEC) in

Il1WL i ns ide the bedrool1!s, drawi ng rooms and kitchens

were found to be I 1 .7 ± 2 .3 , 1 0.8 ± 3 .5 and 1 4. 1 ± 3 .7, respecti vely . Thei r respect ive radon concentration in Bg m- I are esti mated to be 96 ± 1 9 , 90 ± 29 and 1 1 5 .5 ± 3 1 . The values of effective dose equivalent i n mSv Yr- ' i n

these rooms are esti mated to be 4 .8 ± 0.96, 4 .5 ± 1 .5 and

5 .8 ± 1 .5 , respectively. The outdoor radon levels in the oil refinery environment at three d ifferent locations presented in Table 4 are found to be 46 Bq m-l , 4 1 Bq m-l and 22 Bq m-', respectively. This shows that the radon levels in the indoor atmosphere of the refinery are found to be much h igher than those encountered in outdoor environment. The i ndoor radon concentrations i nside the dwel l i ngs also seem to be h igher as compared with other dwell ings of normal background areas' with a mean radon concentration of 54 Bq m-', ranging from 30 to 1 1 4 Bq m-1 . This shows that radon which is present primordial ly in crude oi l and natural gas, is released during different refin ing processes i nto the environment and enhances the environmental radon act ivity outdoors as wel l as indoors.

The results of the measurements of radon and its progeny concentrations in 1 0 different foundries, i .e. lock factories of Al igarh are given in Table 5 . The mean

radon concentration was found to be 60 ± 1 7 Bq m -l with

Table 4 - Radon levels in outdoor environment

SNo Potential Radon conc. A lpha Energy (Bq m-l) conc. ( mW L)

I 5 . 5 46

2 5.0 4 1 3 2.7 22

Average 4.4 36

S .D . 1 .5 1 2

Table 5 - Radon levels inside foundries

SNn No. of Detectors

5

2 6

3 6

4 5

5 7

6 4

7 5

8 5

9 5

1 0 6

Average

S .D.

Potential Radon A lpha conc. Energy ( Bq m-

') conc. (mWL)

5.6 48

6.4 55

7.2 63

6 .8 59

8 .4 73

5 . 5 47

4.4 38

5 .3 46

1 0.7 92

9.3 SO 7 .0 60

2.0 1 7

Effective Dose (mSv Yr·

' )

2.3

2 . 1

1 . 1 1 .8

0.6

Effective Dose (mSv Yr· '

)

2.4 2.X

3.2

3.0

3.7

2.4

2 0

2.3 4.(, 4.0

3.0 O.R

7 () () INDIAN J PU RE APPL PHYS . VOL 37. OCTOBER IlJlJlJ

a minimulll value of 38 Bq m-I

and a Illaximum of 92 Bq Ill-I. The mean radon concentrations in foundries are

found to be comparable with the mean concentrations or 48 Bq m- ' rangin g rrom 29 to 64 I3q m-:1 prevailing in

th e dwellings of Ali garh c ity". The present study point s

out that the rad on levels are Illuch below the United States Environmen t,Ii Protect ion Agency (US EPA ' s) reilled ia I action leve l I" 1'0 1' ex isti ng houses of ISO Bq Ill- I. Thi s al so conc ludes that the radon may not be

responsible for higher lung cancer inciciences. One Illay ha ve to look 1'0 1' the cau se in other pollutants, or these, the i mportan t ones ,Ire s i I ica dust, meta II ic fumes, carbon Illonox ide, pyrol ysi s product s including po ly nuc le,lr aromati c compounds, phenol, formaldchyde, furfury l al cohol. isocyanate and amines ( ingredients in the bind­ers).

4 Conclllsions The study of radon levd s inside an oil refinery and

some roundries ( lock ractories ) arc found to be below the USEPA' s remedial ,Icti on level or ISO I3q Ill- ' .

I-I owcvc 1' , t hc r,l cion concent r;lt ions in oi I rcri neri es seems to be higher in both outcioo r and indoor envi ro n­Illents as compared to those round in normal background dwc llings . The rad on levc ls inside the roundri es in vcs­ti g, lted are or th e samc order as mcasured in dwellings

or the saillc cit y. The enhanccd lung cancer rat cs in

roundri es cannot be attrihuted to r'ldon. Some other po llut ant s Illay bc responsihle.

A ck Ilowlcd gcmelll

One or the authors. CA.IK) thanks CS IR. New Delhi . ror rinanci;iI assi stance in the rorm or Poo l OITicership.

Financial assistance from Mini stry of Environment & Forest, Govt. of India for research projec t is also thank­full y acknowledged.

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