1472.pdf

T

a b l e

o

f

C

o

n t e n t s

Se c t i o n

1

:

L

e a d 1

1 1 In t r o d u c t i o n 1

1. 1. 1 Le a d i n t h e En v i r o nme n t 1

1 2 Su s c e p t i b i l i t y T o Le a d Po i s o n i n g

2

1.3 Le v e l s o f

C

o n c e r n

3

S

e c t i o n

2

:

M

e c h a n i s

m

s o f L e a d

A

b s o r p t i o n a n d It s Ph y s i o l o g i c a l

E

f f e c t s .

7

2. 1 Le a d

A

b s o r p t i o n a n d Bi o a v a i l a b i l i t y

7

2.1 1 Ce l l u l a r

M

e c h a n i s

m

s

9

2.1.1. 1

D

i f f u s i o n 1 0

2.1.

1

.2 Pi n o c y t o s i s 1 1

2.1.1.3

A

c t i v e Tr a n s p o r t 1 1

2.1.2 Bl o o d ,

D

e n t i n e a n d B o n e L e a d 1 1

2.2

D

o s e Re s p o n s e 1 2

2.2.1 A c u t e Ef f e c t s 1 2

2.2

.

2

C

h r o n i c N o n Ca n c e r Ef f e c t s 1 3

2.2.3 Re p r o d u c t i v e/ D e v e l o pme n t a l Ef f e c t s 1 4

2.2

.4

C

a r c i n o g e n i c it y 15

2.3 Ro u t e o f Ex p o s u r e 15

Se c t i o n

3:

S

o u r c e s o f

L

e a d 1 7

3

.

1

Le a d i n Pa i n t 1 7

3.2 Le a d i n

A

i r 1 8

3.2.2 Du s t / So i l 2 0

Se c t i o n

4:

V

a r i a t i o n i n Su s c ept i b i l i t y t o L e a d Po is o n i n g 2 2

4. 1 Po p u l a t i o n s a t Ri s k 2 2

4. 1. 1

C

h i l d r e n 2 2

4. 1. 1. 1 Be h a v i o r a l Fa c t o r s 2 3

4. 1. 1.2 Bi o l o g i c a l Fa c t o r s 2 4

4. 1. 1.3 Fe t a l Su s c e p t i b i l i t y 2 5

4. 1.2 Ol d e r Ad u l t s 2 6

4. 1.

3

O

c c u p a t i o n a l Ri s k 2 7

4.2 Nu t r i t i o n a l St a t u s 2 7

4.2.

1

Ir o n

D

eh c i e n c y 2 8

4.2.

2

C

a l c i u

m D

e f i c i e n c y 2 9

4.3 Se a s o n a l i t y 2 9

4.3. 1 Ph y s i o l o g i c a l

M

e c h a n i s

m

s 3 0

4.

4

So c i o d emo g r a p h i c St a t u s 3 2

4.4. 1. 1 Ra c e/ Et h n i c i t y 3 3

4.4. 1.2 In c ome 3 4

4.4. 1.

3 H

o u s in g

3 5

4.5 Ge n e t i c s 3 6

S

e c t i o n

5

:

C

o n c l u s i o n s 3 9

5. 1

D

i s c u s s i o n 3 9

5. 1. 1

A

g e 4 0

5

. 1.2

N

u t r i t i o n 4 0

5

. 1.

3

Se a s o n a l i t y

4 1

5

. 1.

4

S

o c i o d emo g r a p h i c

St a t u s

4 2

5. 1.

5

G

e n e t i c s 4

3

Se c t i o n 6: Re f e r e n c e s 48

L i s t o f

T

a b l e s

Ta b l e 1 1 Le a d Re g u l a t i o n s 6

Ta b l e 1.2 Le a d

A

d v i s o r i e s a n d Re c o

m m

e n d e d Le v e l s 6

T

a b l e

4

.1

A

c u t e

E

f f e c t s o f

L

e a d

E

x p o s u r e in

C

h i l d r e n 2 6

Ta b l e 4.2 Ch r o n i c Ef f e c t s o f Le a d Ex p o s u r e i n Ch i l d r e n 2 6

Ta b l e 4.3 Ge ome t r i c

M

e a n s o f Bl o o d Le a d Le v e l s b y Ra c e

/

Et h n i c i t y 3 4

T a b l e 4.4

G

e ome t r i c

M

e a n s o f Bl o o d Le a d Le v e l s b y In c o

m

e Le v e l 3 5

T a b l e 4.5

G

e ome t r i c

M

e a n s o f Bl o o d Le a d Le v e l s b y Ag e o f Ho u s i n g

—

3 6

T a b l e

5

. 1 Es t ima t e d Pe r c e n t a g e o f

C

h i l d r e n

(

Li v i n g l n Cit i e s

w

i t h

Po p u l a t i o n s

O

v e r O n e

M

i l l i o n

₎

0.5 -

5

Y

e a r s

O

l d

w

i t h Bl o o d Le a d

Le v e l s Gr e a t e r T h a n _{1 5 /}/g

/

dL b y

R

a c e a n d In c ome 4 2

L i s t o f

F

i g u r e s

Fi g u r e 1.1

C

D C '

s Ac t i o n Le v e l f o r Bl o o d Le a d in Ch i l d r e n 4

Fi g u r e 2. 1

C

o n c e p t u a l

D

l \ g r a

m

o f t h e

M

o v eme n t o f Le a d In t o a n d

T

h r o u g h

t h e Hu

m

a n Bo d y 8

Fi g u r e 2.2 Di a g r a

m

o f V a r i o u s Ro u t e s o f U p t a k e f r om t h e In t e s t i n a l

Lu me n 1

0

Fi g u r e

2

.

3

Ef f e c t s o f In o r g a n i c

L

e a d i n

C

h i l d r e n a n d

A

d u l t s

—

L

o

w

e s t

Ob s e r v a b l e Ad v e r s e Ef f e c t Le v e l 1 3

Fi g u r e 3. 1 H i s t o r i c a l Re l a t i o n s h i p s b e t

w

e e n Le a d i n

G

a s o l i n e a n d Le a d i n

Ai r i n t h e U n i t e d

S

t a t e s 19

Fi g u r e 4. 1 Pe r c e n t a g e o f U.S. Ch i l d r e n 1

-5 Y e a r s o f

A

g e

w

i t h Bl o o d L e a d

Le v e l s Gr e a t e r t h a n o r E

_q

u a l t o 1

0

_/^g

/

dL 2 3

S

e c t i o n

1

:

L

e a d

1.1 In t r o d u c t i o n

Le ad is a b luish

-gra_y

m

etal fo u nd in the e a rth's c r u st a nd do e s n ot o c c u r n atu r a_{l l y}

in hu

m

a n s. T he

m

etal

i

s de n s e,

m

al le a

b

le, r e s

i

sta nt to c o r r o sio n, a nd ha s a low

m

elting

point. T he

m

o st c o

m m

o n fo r

m

s of le a

d

o c c u r a s le ad o x

i

de s, le ad s alts, a nd o rga nic s alts

Du e to its u s e

i

n in

d

u str ial a ct

i

vitie s, le ad ha s

b

e e n d istri buted w i

d

e

l

y, a n d

i

s u

b i

quito u s

in the e n v ir o n

m

e nt toda_y . Hu

m

a n s ha v e le a

d

in their

b

od ie s a s a r e s ult o

f

e xpo s u r e to the

m

a n

m

ade s o u r c e s. Le a

d b i

o a c c u

m

u

l

ate s a n

d p

e r s

i

sts in l

i

vin

g

o r

g

a n

is

m

s. It ha s n o

kn own

_p

h ysio

l

o_{g i}c al fu n ctio n a nd ha s be e n i de nti fi ed a s a to xin in hu

m

a n s. T he to xic

ef fe cts o

f

le ad in the hu

m

a n

b

o_{d y} a r e kn own to c a u s e de v elo_p

m

e nta

l

, n e u r olog ic al,

r e

_p

r odu ctiv e, a nd c el lula r da

m

age

(

Yu

le

, 19 92

)

.

Le ad is c

l

a s s

i fi e

d a s a

_p

rio r

i

t_y

_p

ol luta nt o n t

h

e Su

_p

e r

f

u n

d h

a z a rdo u s wa ste s

it

e s

(

Fede r a

l

Re_{g i}ste r 1 9 9 8

)

. In c r e a s ed he alth c o n c e r n s r ega r d ing le ad e x

po s u r e ha v e

s_{i g}ni fi c a nt_{l y}

d

e c r e a s ed the u s e of le ad in _ga s ol in e, paints, c e r a

m

ic pr odu cts, c a ul

k

ing, a nd

p

i pe s ol de r

(

Hu nte r 19 7 7

)

. De s

p

i

te s u

b

sta ntial r edu ctio n s of le ad e x

_p

o s u r e s o v e r the _pa st

2 5 ye a r s, le ad

p

ois o ning c o ntin u e s to be a s e rio u s he alth r isk , e s

p

e cial

l

y

f

o r ch i l

dr e n

.

C h

r o n

i

c e x

_p

o s u r e s to

lo

w

l

e v e

l

s o

f l

e a

d

a r e a n e n v

ir o n

m

e nta

l

r e a

l i

t_y

in

the United

S

tate s

toda_y

(

N I E H S

/

U S E P A 1 9 9 9

)

. In v e sti gating fa cto r s that c o nfe r

i

nd ivi

d

u al s u s c e

p

ti b i l it y

to

le a

d

to xic

it

_{y i}s

i m p

e r ativ e to s et t

in

_g e n v

ir o n

m

e ntal a nd o c c u

_p

at

io n a

l sta n

d

a r

d

s that a r e

Le ad abate

m

en t _pro_gr a

m

s ha ve be e n stud ied for their e f fe ctiv e n e s s in r edu cin _g

b lo od le ad le v els. Se v e r al stud

i

e s ha v e fo u nd that i

m

pr ope r le ad abate

m

e nt pr a ctic e s c a n

a ctu al l y

i

n c r e a s e le a

d

le v e

l

s in ch i l

d

r e n Re s ults ind ic ate that a n_y t_{y p}e of abate

m

e nt

m

ethod

—

s oi l, du st, paint, a nd edu c atio n al inte r v e ntio n

—

m

u st be tho r o ug h a nd c o ntin u al

in o rde r to be

b

e n e

f

icial. A bate

d

a r e a s o

f

te n

b

e c o

m

e r e c o nta

m

in ate

d

o r a ctu a

l l

y e x

p

o s e

pe o_{p l}e to h i

_g

he r le v els of le ad tha n _pr e

-abate

m

e nt c o nd itio n s Fa v o r ab le r e s u lts cire

m

o st

o

f

te n s e e n w

h

e n a c o

m b

in atio n o

f

_pr o_pe r a

b

ate

m

e nt te c

h

ni qu e s a r e ut

i l i

z e

d

(

I S S I, 199 9

)

.

M

e a s u r

i

n

_g

the a

m

o u nt o

f

le ad in the

b l

o o

d

is c o n si

d

e r e

d

to be t

h

e

m

o st u s eful

s c r e e nin_g a nd d ia_gn o stic te st fo r

l

e ad e x

_p

o s u r e. T h is

m

e a s u r e

m

e nt, r e

f

e r r ed to a s the

b lo od le ad

le v e

l, r ef le cts le a

d

'

s _{d y}n a

m

ic e_qui

li

b

r

i

u

m b

etw e e n a

b

s o r_pt

i

o n , e x c r etio n , a n

d

d

e

_p

o s

i

tio n

i

n s o

f

t- _{a n}

d

h_{a r}

d

-t

i

s s u e c o

m

_pa rt

m

e nts. B lo od le a

d

le v els o

f

te n u nde r r e

pr e s e nt

the total bo_{d y b}u rde n, but they a r e sti l l a w i del y a c c epted

m

e a s u r e

m

e nt of e xpo s u r e to

le a

d

T

h

is

i

s du e to the fa ct t

h

at b

lo o

d le a

d l

e v els r e s_po n

d

r elativ el y r a

_p

i

d l

_y to c

h

a n

_g

e s

in

le ad intake a nd,

w

ith in a l i

m

ite

d

r a nge, ha v e a l in e a r r elatio n sh i p to intake le v els

(

A

T

S D R 1

9 9

2

₎

.

1

.

2

F

a c t o r s t h a t

C

o n f e r

S

u s c e p t i b i l i t y t o

L

e a d

P

o i s o n i n g

T h

e r e is a

m

a rked v a r

i

atio n in s u s c e_pt

i b

i l it_y to

l

e ad-

i

_n d_{u c e}d _{to x}i_{c e}f f_{e cts}

b

_etw _{e e n}

h

u

m

a n

_p

o_pu

l

atio n _gr o u_ps a nd ind iv i du als. B lo od le ad

le v e

ls

m

a

y v a r_y s u

b

sta nt

i

al l y

fr o

m

e x_po s u r e to le a

d

. Ac r o s s po

p

ulat

i

o n s, vci r

i

atio n in he alth ef

f

e cts

m

ay

b

e du e to h i g he r

A ge_;

Oc c u_patio n ;

N

utr

i

t

i

o n_;

S

e a s o n al

i

t_y;

So ciode

m

o_gr a_{p h}

i

c sta_tu s_;a nd

Ge n etic s.

Y

o u n_g c

h i

l dr e n a r e the

m

o st s u s c e_pt

i b

le a_ge _gr o u_p to the ef

f

e cts of le ad

pois o nin_g, fo r both b iolog ic al a nd beha v io r a

l

r e a s o n s. Ce rtain o c c upatio n s

m

ay als o

in c r e a s e the risk of e x_po s u r e to le ad. N utr ie nt—le ad inte r a ctio n s, pa rtic ula rl y w ith

c alciu

m

a nd ir o n , ha v e als o be e n shown to in c r e a s e the b io a v ai lab i l ity o

f

le ad. Se a s o n al

f lu ctu atio n s in

_{b l}

o od le ad le v els ha v e be e n obs e r v ed du rin _g the wa r

m

e r

m

o nths,

s u _{g g}e stin_g that e x _po s u r e a nd abs o r_ptio n of le a

d m

a_y v a r_y s e a s o n

d

l y.

D

e

m

o

gr a_{p h i}c al l y,

p

e o_{p l}e l iv_in_{g i}n

_p

o o r u rba n c o

m m

u nitie s w

i

th o

l d

e r ho u sin

_{g h}

a v e

b

e e n

f

o u n

d

to

h

a v e

h

i

_g

h

e r r ate s of

l

e a_{d p}o

i

s o nin_g. A nd pe r

h

aps

m

o st r e c e ntl y, r e s e a r che r s a r e d is c o v e ring

that _ge n etic _pol y

m

o r_{p h i}s

m

s

m

a_{y b}e r e s_po n si b le fo r c o nfe rri n_g s u s c e_pti b i l it

_y

to lea

d

p

o

i

s o nin

_{g i}

n hu

m

a n s.

1

.3

L

e v e l s o f

C

o n c e r n

T h

e a c tio n

l

e v el

f

o r

b l

o od le a

d

in c

h i

l

d

r e n

h

a s ste a

d

_{i l y}

b

e e n lowe r e

_d

o v e r t

h

e

_p

a st

5 0

_ye a r s. T he C

D C

low e r ed the thr e shol d fo r b lo od le ad in ch

i

l

d

r e n fr o

m 6 0

/J-g

/

d

L to

3

0

//_g

/ d

L

i

n 1

9

7 0, t

h

e n aga

i

n to 2 5 lug /

d

L in 1 9 8 5, a nd to t

h

e c u r r e nt le v e

l

of 1 0 //

g

/ d L in

Fig u r e 1.1 C D C

'

sA c t io n L e v e l f o r Bl o o d L e a d i n Ch i l d r e n

C D C

'

s

A

c

t i

o n

L

e v e

l f

o r

B l

o o

d L

e a

d i

n

C h i ld

r e n

CO

o >

-1

9

6 0-_{1 9 7 0}

1 9 7 0-_{1 9 8 5}

1 9

8

5-1 9 9 1

1 9 9 1-

_p

_{re s e n}t

60 _\i_g

/

d L

3 0 M9 / d L

2 5 Mg

M

I

p

u

g

/ d

₎

-1

1 0 2

0

3 0 4 0 5

0

6

0 7

0

B l

o o

d L

e a

d

Le v e l

p g /d L

A da_{p t}ed fr om F igur e 2, Cas e S tud ie s, A T S D R

Stu d

ie s

ha v e shown that

l i

t tle o r n o

m

a r_{g i}n o

f

s afet_{y w} a s a s s o c

i

ate

d

w

i

th t

h

e ol

d

e r

v alu e s. Betw e e n 1 9 8 6 a nd 1

9

8 8

, s e v e r a

l

stud ie s

(

B el l inge r et al. 1

9

8 7; Sch w a rtz a nd

O t to, 1 9 8 7

)

de

m

o n str ated n e u r obeha vio r al i

m

pair

m

e nt in ch

i l d

r e n w ith

b lo o

d le ad le v e

l

s

a s low a s 1

0

to _{14 p g / d L}, c a u s

i

n

g

the le v el o

f

c o n c e r n to be

l

owe r e

d

to 1

0

|a

g

/ d

L

. A t the

c u r r e nt le v el

₍

1 0 p g

/d

L

₎

, o v e r 1 0

m i l

l

io n

c

h i l d

ren

in

t

h

e

U

.

S

. a r e c o n s

i d

e r e

d

to

b

e at r

i

s

k

fo r le a_{d p}ois o nin_g

(

S

a r_ge n t 1 9

9

5

)

T he a ctio n

le v e

ls

f

o r ele v ated b lo od

l

e ad, u n

d

u e le a

d

abs o r

_p

tio n , le ad to x

i

city, a nd le a

d

pois o nin

g

we r e r e v

i

s e

d

to s e r v e a s

g

ui

d

e

l i

n e s

f

o r le a

d

pois o n

i

n_{g p}r e v e ntio n _pr o_gr a

m

s thr o u

_g

ho ut t

h

e U .

S

.

(

C

D C

M M W

R 2 / 8 /

8 5

)

de_gr e e of u n c e r t ain t_y abo ut the health ef fe cts of le ad is _quite low . It ap pe ar s tha t so

m

e of

the s e ef fe c ts, pa rtic ula rl y cha nge s in the le v els of c e rtain b lo od e n zy

m

e s a nd in a spe cts of

ch

i

l

d

r e n

'

s n e u r obeha vio r al i

m

_pair

m

e nt,

m

a

y

o c c u r at b lo od le ad le v e

l

s s o

l

ow a s to

b

e

e s s e ntial

l

_{y w i}tho ut a thr e shol d Fo r t

hi

s r e a s o n, the A ge n cy '

s R f D

W

o rk Gr o u_p

c o n si

d

e r e

d i

t in a

_p

_pr o_priate to de v elo_p a n R f D fo r in o r_ga nic le ad. E P

A

'

s O f fi c e of A ir

Q

u al it_{y P l}a n n in_g a nd Sta n _da rds, fo r a ha z a rd r a nk ing u nde r Se c tio n 1 1 2

(

g

)

of the C le a n

A

i

r

A

ct A

m

e n

d m

e nts, c o n si

d

e r s le ad to be a "

h i

_g

h

c o n c e r n

"

p

ol luta nt

b

a s e

d

o n s e v e r e

c

h

r o n

i

c to x

i

cit

_y

. Le ad is c u r r e ntl y r egu late

d b y

s e v e r al go v e r n

m

e nt age n cie s

(

Ta

b l

e 1. 1

)

,

T a b l e 1.1

R

e g u l a t i o n s f o r L e a d

A

_ge n c_y *

L e v el Fo c u s Co

m m

e n ts

O SH

A

5 0 Mg /n i^

A i

r Pe r

m i

s s

i b

le Ex_po s u r e L

i m i

t

₍

P E L

₎

:

N

o e

m

_{p l}o_y e

_e

s

e x _po s e

d

to

le a

d

at c o n c e ntr at

io n s

^

5

0 _/U_{g /}

m

^ o

f

a

i

r a v e r a_ge

d

o v e r a n 8

-ho u r _pe r

io

d

E P

A

1.5

A

ir 3

-

_m

o nth a v e r a_ge

O SH A

5 0 /u_{g /}

d

_L B lo o

d

M

e

d

ic al r e

m

o v al

fr

o

m

e x_po s u r e r e_quir ed

C

P

SC

6

_{0 0 p p}

m

(

0.0 6

%

)

Pa

i

nt _{B y}

d

r_y

w

e

i

_g

h

t

A da_pted fr om Summa r_y of sta nda rds a n dr e_gulatio n s fo r le ad

(A T S D R

, 19 9 2

)

T

a b l e 1.2

A

d v i s o r i e s a n d

R

e c o

m m

e n d e d L e v e l s f o r L e a d

A g

e n c_y *

L e v el

F

o c u s

C

o

m

m

e n ts

C

D

C

l O^t_g

/ dL

B

l

o od Le v el of c o n c e r n

f

o r c

h i l d

r e n

A C

G I

H

1 5 0 ^ g /

m

^

A i

r T

i m

e

w

e

i g

hte

d

a v e r a_ge c o n c e ntr at

i

o n

f

o r a n o rmla

l

w

o rk

d

a_y

(

8

hr

a nd 4 0 hr

w

e e

k

)

to w h

i

ch

w

o rke r s

m

a_y

b

e e x _po s e

d w /

o ut a

d

v e r s e e

f f

e cts

(

u n

d

e r

r e v

is

io n

)

C

D

C

(

N

I

O SH

₎

l OO^i_g

/m

^

A i

r Re c o

m

m

e n

d

e

d

Ex_po s u r e L

i m i

t

₍

R

E L

₎

:

A i

r

c o n c e ntr at

i

o n

m

a

in

ta

in e

d

s o t

h

at wo r

k

e r

b l

o o

d

<

0

.

0 6 m g/

l

OO

g o

f

w

h

o

l

e

b l

o o

d

E P A

15

_At

_{g /}

L

W

ate r

F D A

1

0 0

// _g

/ d

a_y Fo o

d

A da_pted fr om Summa r_y ofsta nda rds a nd r e_gulatio n s fo r le ad

(

A T S D R, 19 9 2

)

A C G I H=_{A me ric a n Co n fe r e n c e of Go v e r nme ntal Indu stria}

l H y g ie n ists;C D C=Ce nte r s Fo r D is e a s e Co ntr ol a nd Pr e v e ntio n_; C P S C=Co n s ume r Pr odu ctSafet_{y C}om m is sio n;E P A=En vir o nme ntal Pr ote ctio n _{A g}e n c_y;

F D A=_{Fo oda nd Dr u}

g A d m inistr atio n_;N I O S H=Natio n al In stitute fo r Oc c u_patio n al Safet_ya nd He alth; O S H A=_{Oc c u}

S

e c t i o n

2

:

M

e c h a n i

s

m

s o f

L

e a d

A

b

s

o r p t i o n a n d

I

t s

P

h y s i o l o g i c a l

E

f f e c t s

2

.

1

L

e a d A b s o r p t i o n a n d Bi o a v a i l a b i l i t y

Le ad abs o r_p tio n , o r the uptake of le ad into the cir c ulatio n, is r efe r r ed to a s the

b

io

l

o_g

i

c al a v a

i l

ab

i

l it_y

₍

b io a v ai la

b i

l

i

t_y

₎

o

f

le a

d

T he r e is a _pote ntial

h

u

m

a n ris

k

a s s o ciated

w ith a s ubsta n c e w he n it is del iv e r ed to site s of to xic a c tio n in a b io a ctiv e fo r

m

. T he

b io a v ai lab

i

l it_y of le ad de_pe n

d

s o n

(

M

u sha

k

1 9 9 1

)

:

Si

te of u_ptake

P h ysiolo_g

_y

o

f

u_ptake/tr a n s_po rt to

b

lo od

St

a_ge of

d

e v elo_p

m

e nt

Inte r a ctio n s w ith n utrie nts

S

iz e o

f

_pa rticle s

A m

o u nt e nte r

i

n

_g

the

b

o

d

_y

T he

b

io

l

o_{g i}c a

l

a n

d

_{p h y}s

i

olo_{g i}c a

l

cha r a cte ristic s of a

b

s o r_ptio n, the s ubc el lula r

m

e cha nis

m

s of a

b

s o r_ptio n, a nd the fa cto r s w h ich infl u e n c e abs o rptio n al l

m

u st be

e x a

m

in e

d

to u n de r sta nd the

b

io a v ai la

b il i

t_y o

f

le ad. T he

m

o v e

m

e nt of le ad into a nd

F i g u r e 2. 1

C

o n c e p t u a l D i a g r am o f t h e

M

o v e

m

e n t o f

L

e a d

I

n t o a n d

T

h r o u g h T H E

H

u ma n

B

o d y

Pa i nt

W

ate r

G l T r a ct

Lu n_gs G l T r act

P la s

m

a Extr a-_{Cel lu la r} F l_{ui d}

Ex n aled A ir

P la s

m

a Extr a-_{Cellula r F lu id}

Red B lo od

Cells

O the r Soft

T is s u e s irr at>e c ula r

Bo n e

Co rti c al

Bo n e Kidn ey

[

U rin e

)

- E_{n v} i_{r o n}m_{e n}

tal Me_{d i}a

- B_od y C_om p

a rt me nts

- E lim i_{n a}t i_{o n}

Po ols oftti e Bo_{d y}

- _{Bod y Com pa rtme nto r E lim in at ion Po ol Re}

T he intak e

(

a nd u

_p

take

₎

of le a_{d i}n the _ge n e r al po_pu

l

atio n o ccu r s

m

o st ofte n

thr o u_{g h} the _ga str o

i

n te st

i

n a

l

(

G

I

₎

tr a c t T h is

i

s u s u a

l l

_{y 10} to 1

5

_pe r c e nt of the tota

l

in_ge ste_{d q}u a ntit_y

i

n n o r

m

a

l

adults, but it is h i

g

he r in

p

r egn a nt w o

m

e n a nd ch i l dr e n . T he

in o r_ga nic _{d i}v ale nt fo r

m

o

f l

e ad

(

P b -*

)

is the

m

o st e n vir o n

m

e nta_{l l y} s_{i g}ni f ic a nt che

m

ic al

fo r

m

of the

m

etal. In o r

g

a nic

l

e ad do e s n ot u nde r

g

o b iolo

g

ic tr a n sfo r

m

atio n, w h i le the

o r_ga n ic fo r

m

s of le ad

₍

e _g., tetr a eth y l le ad

)

a r e

m

etabol iz ed in the l iv er Orga nic le ad w a s

p

r e vio u sl y fo u n

d

in _ga s ol

i

n e, tho u g h it is n o lo nge r a n e n v ir o n

m

e ntal c o n c e r n a s a r e s ult

of the

_p

ha s e

-o ut of le aded

_g

a s ol

i

n e

(

A T S D R, 1

9 9

2

)

. T he u

p

take of le ad c a n

i

n clude the

di

v ale nt c at

i

o n o r v a r

i

o u s s o

l

u

b l

e c o

m p l

e x e s.

Si m

u

l

ta n e o u s

l y

, a siz e a

b

le

f

r a ct

i

o n o

f

t

h

e

d iv ale nt le ad io n w i l l fo r

m

r elativ el y in s olub le, e x c r etab le le ad c o

m

p le x e s

(

e.

g.,

h y

d

r o x

i

de, b

i

c a r

b

o n ate

)

.

T

w o i

m p

o rta nt

b i

o

l

o

g i

c al

f

a c to r s w

h i

ch inf lu e n c e the u

p

ta

k

e o

f

le ad in the _{G I} tr a ct a r e the

m

atu rit_y of the _{G I} tr a ct a nd n utrie nt

i

nte r a ctio n s

₍

T R

W

, 1 9 9 4

)

.

2

.1. 1

C

e l l u l a r

M

e c h a n i s

m

s

Se v e r al

m

e cha nis

m

s

b y

w h ich le ad is t

h

o u _g

h

t to be a

b

s o r

b

ed

f

r o

m

the

_g

ut a r e

de_{p i}cted in _{F i g}u r e 2.2. T

h

e s e

m

e c ha nis

m

s in v olv e e nte r o cyte s, the c el ls w h ich l in e the

i

nte stin al w a

l l

.

A

bs o r

ptio n e ntai ls inte r a ctio n s w ith the u_ptake o f e s s e ntial n utrie nts s u ch

F i g u r e 2.2 Di a g r a

m

o f V a r io u s Ro u t e s o f

U

p t a k e f r o m t h e In t e s t i n a l L u

m

e n

P b-_{c o}m p l_{e x}

Lume n

P b+ + P b+ +

T i g h t Jun ctio n

Intermed iate Jun ct io n

"■

4

-L

I

P b-_{ca rrie r}

I

M ic r o villi

P b++

T i g htJu n ction

Te rm in alWeb

_

£)

I

'''" ^ •

—

D) Ente ro c_{y t}e

<: = P b-_{c a n}ie r z :

^

^

|

(<

—

Desmo s ome P b++

>

c

P b+ +

P b+ +

\

r TT T Tf ll l l l l l l l l l l l l l l l l l l l l l iril l l l i l l l l l l l -_&

Inte r c el lula r S pa c e

Ba s eme nt Mem bra n e

So u r c e :

M

o rto n et al. 1 9 8 5

2. I.I . I

D

i

ff

u sio n

O

n e

m

e cha nis

m b

_{y w}

h i

c

h

_le ad

m

a_{y b}e a

b

s o r

b

e

d i

nto the

_g

ut is

d

i f

f

u s

i

o n. T

h

is

m

e cha nis

m i

s driv e n

b y

a c o n c e ntr at

i

o n _gr ad ie nt fr o

m

the lu

m

in a

l

s u rfa c e

l i

nin_g to the

ba s olale r al s u r fa c e

₍

the v a s c ula r si de

₎

. D i f fu sio n

l i k

el y de

p

e nds o n the s olub i l

i

ty

cha r a cte ristic s of the le ad s_pe cie s o

f i

nte r e st, e.

g., t

h

e c o n c e ntr atio n of the io n

i

c o r

u n

b

o u nd le a

_{d i}

o n

(

P

b

^^

)

. It

i

n v o

l

v e s e

i

the r

i

ntr a c e

l l

u

l

a r o r pa r a c e

l l

u

l

a r

m

o v e

m

e n t o

f l

e ad

a c r o s s the c el l w al l. Pa r a c el lula r tr a n spo rt is the

m

o v e

m

e nt of le ad io n s a c r o s s the a r e a

b

etwe e n c e

l l

s c a

l l

e

d

"

t

i g h

t

_j

u n ct

i

o n s

"

2.1.1.2 P in o c ytosis

An othe r

m

e c

h

a nis

m

b y w h ich le ad

m

a_y e nte r the _gut t

i

s s u e is

_p

in o c_yto sis

₍

o r othe r

v e sic ula r

m

e c ha nis

m

s

₎

. In th is

m

e cha n is

m

, the le ad -b

e a rin_g

m

e

d

ia in a l i qui d

m

ic r o

r e_{g i}o n of the _gut is e n_gul fed b y the e nte r o c_yte, o r c e

l

l

m

e

m

br a n e.

T

he e n c aps ulatio n of

le ad

m

a_{y b}e a s olub le o r s u s_pe nded fo r

m

of t

h

e ele

m

e nt,

w

h ich

i

s t

h

e n c a r ried to the

b lo od or site of to xic a ctio n . T h is pro c e s s is si

m

i la r to the ha nd l ing of s ol i d pa r ticle s in

p ha_go c_yto sis

₍

T R

W

,

19 94

)

.

2. 1. 1.

3

Act

i

v e Tr a n spo rt

T he th ir

d

, a n

d p

o s si b l y

m

o st i

m

port a nt, tr a n sport

m

e cha nis

m i

n e n v ir o n

m

e ntal

e x_po s u r e s

i

s e n e r

_{g y}

-

d

_r

i

_{v e n}

, a ct

i

v e tr a n s

p

ort .

T h i

s

m

e c

h

a n

i

s

m i

s r e s

p

o n s

i b l

e

f

o r the

tr a n s_port of c alciu

m

a n d ir o n

_{

e.g., c alciu

m

b ind ing pr otein

[

CaB P

]

o r c al b ind in

D

)

a nd is

u nde r the c o ntr ol of a n e n z_y

m

e

—

c alciu

m

-,

m

agn e siu

m

- d_e

p

e nde nt A T Pa s e. So

m

e

tr a n s_port s_yste

m

s

h

a v e a

h i

_g

h

e r a

f fi

n

i

t

_{y f}

o r le ad tha n

f

o r n utrie nts T

h

e s e c o

m p

o n e nts a r e

r e s_po n si b le fo r the a

b

s o r_ptio n a nd r e_gulatio n of

b

lo o

d

c alciu

m

le v els a nd take

_p

la c e in t

h

e

ba s olate r al

m

e

m b

r a n e of

m

u c o s al e_{p i}thel ial c el

l

s

(

T R

W

, 1 9

94

)

.

2.

1

.

2

B

l o o d

,

D

e n t i n e, a n d B o n e l e a d

On c e le ad e nte r s the b lo odstr e a

m

it is _pr

i m

a r

i l

_y

d i

stri

b

ute

d

a

m

o n_g thr e e

c o

m p

a rt

m

e nts :

b l

o o

d

, s o

f

t t

i

s s u e, a n

d m i

n e r a

l i

z

i

n

g

tis s u e.

T h

e

b

o n e s a n

d

te et

h

o

f

a

d

u

lt

s

c o ntain

m

o r e tha n

9

5

_p

e r c e nt o

f

the total le ad in the bod y. T he le ad w h ich is in the

m i

n e r a

l i

z

i

n

_g

t

i

s s ue

m

a

_y

a c c u

m

ulate in s u

b

c o

m p

art

m

e nts

w h i

c

h d i f f

e r

i

n t

h

e r ate at w

h

ic

h

le ad is r e s o rbed. In

b

o n e

, the r e

i

s a lab i le c o

m

po n e nt, w h ich r e a

di l y

e x cha nge s

l

e a

d

w it

h

sin_{g l}e ex _po s u r e stud ie s, le ad ha s a hal f

-l i fe

(

in adults

₎

of 2 5 da_ys in b lo od, 4 0 days

i

n s o

f

t

tis s u e, a nd o v e r 2 5 ye a r s in the n o nlab i le po rtio n of t

h

e bo n e

(

A T S D R, 1 9 9 2; Rab in ow itz

et al 19 7 6

)

.

L e a

d

e x

_p

o s u r e c a n be e v alu ate_{d b y}

m

e a s u rin

_g

e r_ythr o c_yte _pr oto

_p

o r

_p

h yrin

₍

E P

₎

, a

c o

m

_po n e nt of r ed b lo od c el ls w h ich c o ntain s 9 9 pe r c e nt of le ad in b lo od

(

the r e

m

ainin

_g

o n e _pe r c e nt is fo u n

d i

n the

_{p l}

a s

m

a

₎

. T h is

m

ethod is c o

m

m

o nl

y

u s e

d

to s c r e e n c

hi l

dr en

f

o r ir o n defi cie n c_y a n

d l

e a_{d p}ois o nin_g

M

ethods to

m

e a s u r e

l

e ad in te eth o r bo n e s

b

_y

X

-r a_y

f

lu o r e s c e n c e te chni qu e s a r e c u r r e n t_{l y b}e

i

n_g

de v e

l

o

_p

e

d

(

T

T N

W

eb, U A T

W

)

.

2

.

2

D

o s e

R

e s p o n s e

So

m

e o

f

t

h

e c el lula r a n_{d p}

h

_ysiolo_g

i

c ef fe cts o

f

chr o nic le ad e x_po s u r e at the lowe st

obs e r v ab le b lo od le ad le v els in ch i l dr e n a nd adu lts a r e _pr e s e nte_{d i}n F i

_g

u r e 2.3.

2.

2

.1

A

c u t e

E

f f e c t s

A

c ute e x

_p

o s u r e s to le ad at

b

lo od le a

d

le v e

l

s _gr e ate r tha n 1 2

5

_ju

_g

/ d L

m

a_y c a u s e

de ath in ch i l dr e n . Br ain a nd k i dn ey da

m

a

g

e ha v e be e n r e

p

o rted in

b

lo o d le a

d l

e v els at

a_{p p}r o x i

m

ate_{l y 10 0 /}/ _{g /}

d

_{L i}n adults a nd 8 0 // _{g / d L i}n ch i l dr e n . Ga str ointe stin al ef fe cts

ha v e be e n a s s o c

i

ated w ith a c ute e x

_p

o s u r e s a r o u nd 6 0 _yU_{g / d L i}n adults a nd ch i l dr e n

Fig ur e 2.3 Ef f e c t s o f I n o r g a n i c L ea d in Ch il d r en a n d A d u l t s

—L

o

w

e st

O B S E R V A B L E

A

D V E R S E EF F E C T SL E V E L

L

e a

d C

o n c e n

t

r a

t

i

cx i

i

n

B ic x x

l

u

_{g ^d L}

Ch ild

r e n

BTc e_{p h}alo_path_y ■

Ne_pht o_path_y ■

Ra nk ATe nia

Cd ic

-He nn

_^

obin_{S y}nt he sis

i

-W

amn D l\/t!tabollsm

i

B y thnx_yte Nave Cdndu ct io n

Roto_phor_yin

A

Vfe lod t_y

'

f

W

a rrin D i

IVfete bd ism

f

(

^

)

IQ

He a

ri

n

_g

Q

-o wth '

Dev elo_pme ntal

Toxic_ity

T ran s_pla c e r ital

T ran sfe r

15 0

100

5 0

40

3 0

2

0

1

0

A

du

l

t

s

-Bx e_phalo_path_y

-F_{ra n}kA_{n e n}i_a

■

t

f lemo

_^

obnS_ynthe sis

Re_{ri ph}e rai Ne u r o_path ie s

i

^

I_nf_ert ilit

y

(

me n

₎

Ne_{ph ro p}atti_y

♦

SystolicBo od P res s ure

₍

men

₎

1

He arin_gA x i t_y

_

A

Erythro cyte Pr otop ho ry in

^

(

men

₎

A

B ytfir oc_yteProto_pfx jr_{y i}n

"

(

w ome n

)

-

A

_h

y

perte n sio n

₍

?

₎

In c r e a s ed

Fi r ct lo n

De crea s ed Rr ctio n

A d

^

ed fr om AT SD

R

To xic olo_{g l}c al Profi lef a Le ad

(

198 9

)

2.2.2

C

h r o n i c

N

o n

C

a n c e r

E

f f e c t s

L o n_g te r

m

e x _po s u r e to

l

e a

d i

n

h

u

m

a n s ha s

b

e e n a s s o ciated w

i

t

h b l

o od e

f f

e cts,

yUg / d L in ch i l dr en .

N

e r v o u s syste

m

ef fe c ts hav e be en n o ted in worke r s w ith b lo od lead

le v els of 4 0 to 6 0 _yU_{g / d L} . S lowed n e r v e c o ndu ctio n in pe ri p

h

e r al n e r v e s o c c u r s at b lo o

d

le ad le v els of 3 0 to 4 0 _yU_{g / d}

L

in adults, w h i le n e u r oto xic ef fe c ts in ch i l dr e n a r e tho ug ht to

o c c u r at b lo od le ad le v els o

f

1 0 to 3 0 _/xg/d L o r lo we r. C h i l dr e n w ith b lo od le ad le v els of

1 0 to 5 0 _/i _{g / d L h}a v e be e n shown to ha v e de c r e a s ed I

Q

s c o r e s. Yu le

(

19 9 2

)

s u g ge sted that

the detri

m

e ntal ef fe cts of le ad o n n e u r otr a n s

m

it te r s

m

a_{y b}e a c a u s e of at te ntio n d is o rde r s

a n

d

h y

_p

e r a ctivit

_y

in c

h i ld

r e n. C hr o nic e xpo s u r e to le ad in hu

m

a n s c a n als o r e s u lt in

pr ob le

m

s in

b

lo od

_p

r e s s u r e,

k i d

n ey fu n ctio n, a nd vita

m

in

D m

etabol is

m

(

T T N

W

e

b

,

U

A

T

W

)

.

2

.

2

.

3

R

e p r o d u c t i v e

/

De v e l o p

m

e n t a l

E

f f e c t s

In

m

ale wo rke r s, a c u te a n

d

chr o nic e xpo s u r e s to le a

d

ha v e r e s ulte

d i

n a si gn

i f i

c a nt

de c r e a s e in s_pe r

m

c o u nt a n

d d

e

_p

r e s s ed fu n ctio n of the _pr o state a nd /o r s e

m

in al v e s

i

cle s at

b lo od le a_{d l}e v els of 4 0 to

5 0

/U_{g / d L} . In wo

m

e n , spo nta n e o u s abo rtio n is tho ug ht to be

a s s o ciated w ith a c ute a n

d

chr o nic o c c u_patio n al e x_po s u r e to

h

i g h le v els of le ad

₍

tho u_{g h}

the lowe st

l

e v el at w h ich t

h i

s o c c u r s ha s n ot _yet

b

e e n e stab l

i

shed

) (

X inta r a s 19

9

2

)

.

De v elo_p

m

e ntal ef

f

e cts fr o

m

le ad e x

_p

o s u r e in clude t

h

e in c r e a s e

d

risk of

_p

r ete r

m

del iv e r_y, low

b i

rth wei g ht, a nd i

m

pair e

d m

e ntal de v elop

m

e nt. T he s e e

f

fe cts

h

a v e

b

e e n

n ote

d

at

m

ate r n a

l b l

o o

d l

e a

d

le v e

l

s o

f 10

to 1

5

_//_g

/ d L

, a n

d m

ay

b

e po s si

b l

y

l

owe r t

h

a n

th

i

s

(

Y u

le

19 92

)

. T

h

o u

g

h

h

u

m

a n stu

d ie s

h

a v e t

hu s

f

a r

b

e e n

i

n c o n c

l

u s

i

v e

, a n

i m

a

l

stu

d i

es

2.2.4 Ca r cin o gen i c it y

T he De_pa rt

m

e nt of H e alth a nd Hu

m

a n Se r v

i

c e s

(

D

H

H

S

)

ha s dete r

m

in e

_d

that le ad

a c etate a nd le a

d p h

o s

_{p h}

ate

m

a_y r e a s o n a_{b l y}

b

e c o n si de r ed to be c a r cin o_ge n s ba s ed o n

a ni

m

al stud ie s. K i dn e

y c a n c e r in r ats a nd

m

ic e fr o

m

e x_po s u r e to le ad v ia the o r al r o u te

ha s be e n r e_po rted

₍

C

a

l

a

b

r e s e a nd Ke n_yo n 1

9 9

1

₎

.

F

o u r

m

a

j

o r stu

d i

e s

h

a v e

b

e e n do n e o n wo r

k

e r s e x

_p

o s e

d

to le ad a n d the a s s o c

i

ate

d

risk of de v elo

_p

in

_g

c a n c e r. T wo of the s e stu

d

ie s

d

i d n ot

fi

nd a n a s s o ciatio n

b

etw e e n le a

d

a n d de v elo_p

m

e nt o

f

c a n c e r

(

D in_{g w}al l

-Fo rd yc e a n

d

La n e, 1 9

6

3;N els o n et al. 1

9 8

2

)

; o n e

stu_{d y f}o u nd a n in c r e a s e

d i

n ci de n c e of r e s_{p i}r ato r_y tr a ct a nd k i dn e_y c a n c e r s

₍

Sele v a n et al.

1

9

8 5

₎

; a nd the fo u rt

h

s tud y fo u nd e x c e s s e s fo r lu n_g a nd sto

m

a ch c a n c e r s

(

Co o_pe r a nd

Gaf fe_{y 1 9 7 5;} Gaf fe_y

_[

u_{p d}ate

_]

1 9 8 5

₎

. T he r e s ults of the s e stud ie s we r e l i

m

ited b y the fa ct

that r o ute a n

d l

e v els o

f

e x

_p

o s u r e s to the wo rke r s we r e n ot r e

_p

o rte

d

. A d

d i

tio n a

l l y

, t

h

e

wo rke r s in the s e stu

d

ie s we r e

l

i

k

e

l

_y e x _po s ed to s u

b

sta n c e s othe r tha n le ad. T he r efo r e,

the r e is c u r r e nt_{l y i}n ade

_q

u ate e vi de n c e to dete r

m

in e le ad'

s c a r cin o

_g

e n icit_{y i}n hu

m

a n s.

E

P

A h

a s c

l

a s si

fi

e

d

le a

d

a s a

G

r o u_{p B 2} c a r cin o_ge n, in

d i

c ating that it is a pr o

b

a

b

le

h

u

m

a n

c a r cin o

_g

e n a n

_d

s u

f f i

c

i

e nt a n i

m

al e vi de n c e o

f

c a r c

i

n o

_g

e nicit_y e x

i

sts. T e n r at a s s ays a n

d

o n e

m

o u s e a s s a_{y h}a v e shown statistic a_{l l y} si

g

ni f ic a nt in c r e a s e s in r e n al tu

m

o r s w ith

d i

eta r_y a nd s u

b

c uta n eous e x

_p

o s u r e s to s e v e r a

l

s o

l

u

b l

e

l

e a

d

s alts

(

I R

I

S

, 1

9 9 9

)

.

2

.

3

Ro u t e o f

E

x p o s u r e

Hu

m

a n e x_po s u r e to le ad o c c u r s _pri

m

a ri l y thr o u_{g h} a c o

m b i

n atio n o

f

inhalatio n a nd

o r al r o ute s. Le ad e xpo s u r e u s u a

l l

y o c c u r s thr o ug h t

h

e

i

nhalatio n r o ute in ol

d

e r c

h i l

dr e n

(

L an_{p h}e a r et al. 1 9 9 8

)

. Fo r o c c upatio n al l y expo s ed gr o ups, the inhalation ro ute

c o ntri bute s a _gr e ate r _pr o_po rtio n o

f

the do s e, w h

i l

e t

h

e o r al r o ute is the pri

m

a ry r o ute of

e x_po s u r e to le ad in the _ge n e r al po_pulatio n T he ef fe cts of le ad a r e _qu al itativ e_{l y} the s a

m

e

r e_ga rd le s s of w hethe r the r o ute of e x_po s u r e is inhalatio n , o r al, o r both

(

T T N

W

eb,

S

e c t i o n

3

:

S

o u r c e s o f

L

e a d

3.1 L e a d i n Pa i n t

T he

C

o n s u

m

e r Pr odu ct Safet_{y C}o

m m i

s s

i

o n

b

a n n e

d

t

h

e a

d d

itio n of le a

d

to

i

nte r

i

o r

a n d e xte rio r r e si de ntial

_p

aint in 1

9

7 8

(

Sta e s et al. 1 9

9

4

)

. Paint

, b y r egulatio n ,

m

u st

c o ntain n o

m

o r e tha n ₀.0 6 pe r c e nt

(

6 0 0 pa rts pe r

m

i l l io n

[

p p

m

] )

le ad b y dry wei g ht

So

m

e

_p

aint

m

a n u

f

a ctu r e

d fo r

i

ndo o r u s e in the 1 9 4

0

'

s c o nta

i

n e

d m

o r e tha n

5 0 p

e r c e nt

(

5 0 0,0 0 0 p p

m

)

le a

d

.

Le ad-_b

a s ed paint c o ntin u e s to be a s o u r c e of le ad e x _po s u r e a nd a s_y

m

_pto

m

atic le a

d

pois o nin_g toda_y. It is the

m

o st c o

m m

o n s o u r c e of h i g h

-d_{o s e} l_{e a}

d pois o nin_g a

m

o n_g

ch i l

dr e n

in the

U

.

S

. In ur

b

a n a r e a s, t

h

e

m

a

i

n s o u r c e o

f l

e ad

p

o

is o

ning in ch

i l d

r e n

i

s t

h

e

in_ge stio n o f le ad-b_{a s e}

d p

a

i

nt w

h

ich is _pe el in_g,

f l

a

k in

g

, a nd ch i

p p

ing

(

Fr e u

d

e n

b

u r

g

,

19 8 7

₎

. It is e sti

m

ated that 7 4

p

e r c e nt of al l pr e

- 1 9 8 0 h_{o u s}i_n

g u n

it

s, ap pr o xi

m

atel y 5 7

m i l

l

i

o n u n

i

ts, c o nta

i

n

l

e a

d

-

b

_{a s e}

d

paint in t

h

e

U

.

S

.. It

i

s a

l

s o e st

i m

ate

d

t

h

at c

h i l d

r e n a r e

e x

_p

o s ed to n o n

-inta c t

_p

a

i

nt o r h i g h du st le ad le v els in 3.8

m

i l l ion ho

m

e s

(

St

a e s et al.

1 9 9 4

)

.

A

m

itai et al.

(

19 9 1

)

f

o u nd that r e

m

o v

in

g

le a

d

-b_{a s e}

d p

a

i

nt b y v a rio u s

m

ethods wa s

ef fe ctiv e in r edu cin_{g b l}o od le ad le v els in ch i l dr e n w ho had at le a st o n e b lo od le ad

m

e a s u r e

m

e nt >_{2 5 |}J_{g / d L} , a nd

l

e v e

l

s r e

m

ain e

d

low e r

i

n the

8

-

_m

o nth fol low

-u_p to t

h

e

r etr o s_pe ctiv e _paint abate

m

e nt stud y. Re s ults

f

r o

m

the Balti

m

o r e Tr ad

it

i

o n al a nd

M

o

d

i f ie

d

Le a

d

-B_{a s e}d P_ai_nt A

b

_ate

m

_{e nt} S_tu

d y

(

Fa r

f

e

l

et al. 1

9 90

)

w e r e n ot a s

f

a v o r a

b l

e.

afte r inte r v e ntio n, we r e n ot s

i g

ni

f

i c a ntl y lowe r tha n pr e

-a

b

ate

m

e nt le v els six

m

o n t

h

s

l

ate r.

A d d itio n al l y , le ad du st le v els

i

n tr e ated ho

m

e s te nded to in c r e a s e

Le ad-b_{a s e}d p_ai_{n t r e}

m

_{o v a}l _{c a n} b_{e a n e}

f f

_{e c t}i_{v e}

m

_et

h

_o

d

_to l_ow_{e r} l_{e a}d l_{e v e}l_s

i

_{n o}

l d

_{e r}

h

o

m

e s

C

ha r n e_y et a

l

.

(

1

9 8 3

)

n oted that i f the a

b

ate

m

e nt

m

ethod is n ot tho r o u

g

h a nd

c o ntin u al, the du st le v els

m

ay w o r sen a s the ho u sing c o nd itio n s w o r s e n

—

a ctu al l y

i

n c r e a s

i

n_g e x

_p

o s u r e

l

e v e

l

s.

3

.

2

L

e a d i n

A

i r

hi c o

m

m

u n

i

tie s w

h

e r e t

h

e r e a r e _point s o u r c e s, s u ch a s s

m

elte r s a nd a s s o c

i

ated

wo rks

{

i.e.

, slag du

m

ps

)

, the le ad c o n c e ntr atio n in s oi l a nd air de c r e a s e s e xpo n e ntial l y

w ith d ista n c e fr o

m

t

h

e s o u r c e.

E

xte rio r

d

u st le ad fr o

m

the s e s o u r c e s

m

ay a c c u

m

ulate o n

o utsi de w al ls, r o ofs, a n

d

v egetatio n

(

Cal de r et al. 1 9

9

4

)

.

M

o st of the le ad in s oi l c o

m

e s

f

r o

m

the de_po sitio n of pa rticle s fr o

m

the air

₍

_A

_{T S D R T}o xF A

Q

s

)

So u r c e s of inte rio r

d

u st in clude c r a cks a n

d

o_pe n s_pa c e s w h

i

ch al low

d

u st le a

d

to e nte r ho

m

e s, w h i le hu

m

a n s

a n

d

a ni

m

a

l

s

m

a_y tr a n s

_p

o rt

l

e a

d

c o nta

m i

n ate

d

s o

i l i

n

d

o o r s. Inte rio r

d

u st a c c u

m

u

l

ate s o n

c a r

_p

ets, s oft fu r nish

i

n gs, a nd

d

u sty a r e a s of the ho

m

e

(

C

al de r et al. 1 9 9 4

)

. Toba c c o

s

m

o

k

e is als o a s o u r c e o

f l

e ad

i

n the air

₍

Ra

b i

n ow

i

tz et al. 1

9

7

6

)

.

Pa rticle s w h ic

h

a r e

_g

r e ate r tha n 2.5

m i

c r o n s a r e de

p

o site

d i

n the ci l iate

d

r e

g i

o n s

of the r e s

_p

ir ato r

_y

tr a ct w he r e the_y a r e

_p

a s s ed to the

G

I tr a ct _{b y} the

m

u c o c

i l i

a r_{y l i}

f

t

m

e cha n

i

s

m

. S

m

a

l

le r

T he E P A r e

_q

u

i

r e s

l

e a

d

in air n ot to e x c e ed 1.5 |Jg /

m

^

a v e r a_ged ove r 3

m

o nths.

T he o utdo o r air le ad c o n c e ntr atio n _pr o vi de s a la r_ge _pa rt o

f

the total air le ad e x_po s u r e_;

c o n si de rin_g that the indo o r air le ad c o n c e ntr atio n is t_{y p i}c a_{l l y} abo ut _{3 0 p}e r c e nt of the

o utdo o r c o n c e ntr atio n

f

o r the _ge n e r a_{l p}o

_p

ulatio n

(

U S E P A 1

9

8 6

₎

.

Ga s ol in e c o

m

bu stio n ha s h isto ric al l y be e n the

m

a

_j

o r s o u r c e of airbo r n e le ad in the

e n v ir o n

m

e nt. T

h

e

U

.

S

.

g

o v e r n

m

e nt

p ha s ed o ut the u s e o

f l

e a

d

e

d

_ga s ol in e in 19 7

6 i

n

o rde r to r edu c e _pote nt

i

a

l

l y ha z a rdo u s c o n c e ntr at

i

o n s of le a

d i

n a

m

b ie nt air

₍

P

i

rk

l

e et al.

1 9 9 4

₎

. In 1 9 9 0, Co ngr e s s pr oh i b ited the u s e of le ad o r le ad ad d itiv e s in ga s ol in e a

f

te r

D ec e

m

be r 19 9 5 a s _pa rt of the C le a n A ir A ct A

m

e nd

m

e nts

₍

U S E

P A , 1 9 9 8

)

. T he r e s ult of

th is le_{g i}slatio n wa s a s

i g

n i fi c a nt r e

d

u ctio n in a

m

b

i

e nt air c o n c e ntr at

i

o n s betwe e n t

h

e

ye a r s 1 9 7 0

-1 9 9 0

₍

F

i

_gure 3.1

)

. A

l

tho u

g h le a

d f

r o

m

_g

a s o

l i

n e is n o

l

o n_ge r c o n si

d

e r e

d

to

b

e

a _pu

b

l ic he alt_{h p}r o

b l

e

m

,

l

e a

d

fr o

m p

a st a uto

m

o

b i l

e e

m i

s s

i

o n s c o ntin u e s to

p

e r s

i

st

i

n s o

i l

(

A

T S D R , 19 9 2

)

.

Fi g u r e

3

. 1

H

i s t o r i c a l

R

e l a t i o n s h i p b e t

w

e e n L e a d i n

G

a s o l i n e a n d

L

e a d i n

A

i r i n t he

U

n i t e d

S

t a t e s

Ymt

3.2.2 Du s t

/ S

o i l

T he a

m

o u nt of le ad in du st a nd s oi l is c o n si de r ed to be the s u

m

of le ad fr o

m

le aded paint, ga s ol in e c o

m

bu stio n a nd statio n a ry s o u r c e s in the s u r r o u nd ing a r e a

(

C

D

C

M M

W

R 8 / 1 9 / 8 8

₎

. Du st a nd s oi l abate

m

e nt ha v e

p

r o v e n to be d i f f ic ult a n d ofte n u s ele s s,

i f n ot detri

m

e ntal, to de c r e a sing le ad e xpo s u r e. In a stud y b y

H

i lts et al

(

1 9 9 5

)

, H i

g

h

E f f icie n c_{y P}a rtic ulate

A

ir

₍

H E P A

₎

v a c u u

m

in_g of f lo o r s in si de ho

m

e s in the s

m

elte r

c o

m m

u nit_y e v e r_y six we ek s w a s n ot fo u nd to si gn

i

f ic a ntl

_y

lowe r b lo o

d

le ad le v els in

ch i l dr e n . In fa ct, r e c o nta

m

in atio n wa s tho ug ht to ha v e o c c u r r ed betw e e n v a c u u

m i

ngs.

I

n

the s a

m

e stu

d

_y, a c o r r elat

i

o n w ith lowe r

b

lo od

l

e a

d l

e v els we r e

f

o u nd in ch

i

l dr e n w

h

o s e

fa

m i

l ie s r e

m

o v e

d

sho e s at the

d

o o r, a n

d

in c r e a s e

d b

lo o

d l

e ad le v e

l

s we r e

f

o u nd in

ch i l dr e n w it_{h p}ets. T

h

e in v e st

i

gato r s a s s o ciated the s e f in

d

ings w it

h

the tr a n spo rt of le ad

-c o nta

m

in ate

d

s oi l indo o r s. Inte r v e ntio n s in lowe r r

i

sk a r e a s, fu rthe r

f

r o

m

le ad point

s o u r c e s

{

e.g., s

m

elte r s

)

, te nd to be

m

o r e ef fe ctiv e, sin c e r e c o nta

m i

n atio n n e a r the s o u r c e

is

m

o r e si gni f ic a nt in r e

-ele v atin_{g b l}o od le ad le v els

₍

C al

d

e r et al. 1 9 9 4

)

.

3

.

3

L

e a d i n

F

o o d a n d

W

a t e r

H isto ric al l y le ad e x _po s u r e ha s c o

m

e fr o

m m

a n_y s o u r c e s, in clu

d

ing the d ir e ct

atmo .s

p

he ric de

p

o sitio n of le a

d

to s oi l a nd fo od, a nd fr o

m,

c a n s w ith le ad

-s ol de r ed s e a

m

s

Le ad c o nta

m

in atio n in ho

m

e_gr own fr uits a nd v e_getab le s

m

a_y a

l

s o

b

e the r e s ult of

at

m

o s_{p h}e r

i

c de_po sitio n o

f

le a

d

to the s oi l in w h

i

ch the

_y

a r e

_g

r ow n. T he Fo od a nd

D

r u

g

A d

m

inistr atio n ha s

m

ade si gni

f

i c a nt _pr o_gr e s s in r edu cin_{g l}e ad in fo od pr o c e s sin_{g i}n the

so

m

e c a s e s even "

s afe"

c e r a

m

ic w a r e

m

a_y be co

m

e ha r

m

ful i f the _gla z e c h_{i p}s or flak e s off,

e x _po sin_{g l}e ad-_{c o n}t_ai_ni_n

g p i g

m

e nts

₍

A T S D R , 19 9 2

)

.

Le ad in wate r

m

a_y o ri g in ate fr o

m

le ad p

i

_pe s o r le ad s ol de r ed

f i

t t

i

n _gs u s ed in the

p lu

m

b in _g of s o

m

e ol de r ho

m

e s. D ir e ct c o n s u

m

ptio n of, a nd /o r c o o

k

ing in , le ad

-c o nta

m

in ated w ate r

m

a_y als o le ad to in c r e a s ed le ad e x_po s ure T he E P A c ur re nt_{l y l i}

m

its

l

e a

d i

n

d

r

i

n

k i

n_{g w} a t er to 1

5

_\x

g/

L . T

h

e

C

o n s u

m

e r Pr o

d

u ct

S

a

f

ety

C

o

m m

is s

i

o n

(

C P S C

)

,

the E P A , a nd s ele cted State age n cie s c o ntr ol the le v els of le ad in drink ing w ate r c o ole r s.

O

l de r wate r c o ole r s t

h

at a r e

f

o u n

d

to r ele a s e le a

d

a r e e

i

t

h

e r r e c al led o r r e_pa

i

r ed. New

c o ole r s a r e r e_quir ed to be le ad-f_{r e e}

. Fu rthe r

m

o r e, drink ing w ate r in s cho ols is r equir ed to

be te sted r e

_g

ula r

l

_y

f

o r le ad

(

A

T

S D R To xF A

Q

s

)

. T he s e ef fo rts ha v e s

i g

n

i f

ic a ntl y

de c r e a s ed the _pu

b l i

c

'

s da

i

l y le ad intake,

b

ut E P A e st

i m

ate

d

t

h

at 2 4 1,

0

0 0 ch

i l d

r e n le s s

tha n six _ye a r s of a_ge ha v e b lo o d le ad gr e ate r tha n 15 p g

/

d L du e to ele v ated

c o n c e ntr atio n s of le ad in drink in_{g w} ate r

(

C D C

M M W

R 8 / 1 9 / 8 8

)

.

T he a

m

o u nt o

f d i

eta r_y

l

e ad abs o r_ptio n is n ot

k

n own T he r e

i

s e v i de n c e fr o

m

stud ie s that the a

b

s o r_ptio n of le ad fr o

m

fo od c o n s u

m

_ptio n b y in fa n ts

i

s 4 0 to 5 0 pe r c e nt

o

f

the a

m

o u nt of

l

e a

d i

n the

f

o od. T he E P

A

(

1

9 8 9

)

e st

i m

ate s th is r a n

g

e to

b

e a

b

o ut

4 2

to

5 3 pe r c e n t. T he

b

io a v ai lab i l ity of le ad s alts in drink ing w ate r is h i g h w he n c o n s u

m

ed

b

etw e e n

m

e a

l

s.

T h

e

m

a x

i m

u

m

r ete ntio n of le a

d i

n c

h i

l dr e n

i

s e st

i m

ate

d

to

b

e abo ut

6 0

pe r c e nt o n a n e

m

_pt

_y

sto

m

a c

h

, a nd abs o r

p

tio n is c o n si de r ed to be s o

m

ew hat s

m

al le r tha n

S

e c t i o n

4

:

V

a r i a t i o n i n

S

u s c e p t i b i l i t y t o

L

e a d

P

o i s o n i n g

4.1 Po p u l a t i o n s a t

R

i s k

4

. 1.1

C

h i l d r e n

Ce rtain _po_pulatio n s a r e

m

ore s u s c e_pti b le to le a_{d p}ois o nin

_g

tha n othe r s. In

c o

m

_pa r

i

s o n w ith the n o r

m

al adult _po_pulatio n , ch i l

d

r e n u n

d

e r the age o

f

s e v e n a r e at

m

u ch

h i g he r r

i

sk o

f l

e a

d p

o

i

s o n

i

n_g. A c o

m b

in atio n of intrin sic beha vio r al e xpo s u r e a n

d

b iolo_{g i}c al fa cto r s

m

ake ch i l dr e n

m

o r e v uln e r a

b

le t o le a

d

e x

_p

o s u r e.

T h

e _pe r c e nta_ge of ch

i l

dr e n betw e e n t

h

e a_ge s of o n e a nd

fi

v e w ith b lo o

d l

e a

d

le v els > ₁₀

yUg / d L ha s

d

e c r e a s ed dr a

m

atic a

l

l y o v e r t

h

e pa st 2

0

ye a r s w

i

th

m

o r e pub l ic

awa r e n e s s a nd r e_gu lat

i

o n r e_ga rd in_g the da n_ge r s of le ad e x_po s u r e. A c c o rd in g to

d

ata fr o

m

the Natio n al H e alth a nd N utr

i

tio n Ex a

m

in atio n Su r v e_y

₍

N H

A N

E

S

₎

'

11a nd H I, t

h

e

e sti

m

ate s

d

r o

_{p p}

e

d f

r o

m

8

8

.2 pe r c e nt

i

n 1

9 7 6

-

19 8 0

_to 4

.4

p

e r c e nt

i

n 1

9 9

1

- 1

9 9

4

(

F i g

u r e

4. 1

)

. P ha s e tw o of N H A N E S

m

(

1 9

9

1

- 1

9

9 4

)

data

i

de nti fi ed 2.2

p

e r c e nt of the

p

opulatio n

o v e r the a_ge of 1 w

i

t

h

b lo od le ad le v e

l

s > ₁₀

/Ug / d L a nd a

m

e a n o

f

2.3 /zg /

d

L . T

h

e data

als o i

d

e n t

i f

ied 4.4 pe r c e nt of

U

.

S

. c

h i

l dr e n

b

etwe e n the a

ge s o

f

o n e a n

d f

iv e _ye a r s w ith

b lo od le ad le v els > 1

0

_/U_{g / d L} a nd a

_m

e a n of 2.7

// _{g /}

d

L . T h is pe r c e ntage

d

e n ote s that

8 9 0,0 0 0 ch i l dr e n in the U S. had ele v ated b lo od le a

d

le v els

(

P irk

l

e 1 9

9 8

)

. T he r e w a s als o

Fi g u r e 4.1 Pe r c e n t a g e o f U .S. Ch i l d r e n 1

-5 Y

e a r s o f Ag e

w

i t h Bl o o d L e a d

L

e v e l s

G

r e a t e r t h a n o r _{E q}u a l T o 1 0 //g /d L

P

e r c

e

n

t

a

_g

e

o

f U

.

S

.

C

h i l

d

r e n

1

-

5 Y

e a r s

o

f A

g

e

w

i

t

h

B l

o o

d L

e a

d L

e v e

l

s

G

r e a

t

e r

t

h

a n o r

E q

u a

l

T

o

1

0 p g / d L

c

0 )

x: O

o

0 )

s

a >

o

I—

0 ) 1 0 0

9 0

8 0 7 0

6 0

50

40

3 0

2 0 1 0

0

_

8

a

2

_

8

.

9

-4

:

4

-1 9 7 6-1 9 8 0

N H A N E S I I

1 9 8 8-1 9 9 1 19 9 1-1 9 9 4

N H A N E S

A dap ted fr om C D C'

s Le adPois o nin_g Pr e v e nt io n Pr ogr am Fa ct She et

v a r ia

b

i l it_y

i

n b lo od le ad le v els a

m

o n_g ch i l dr e n betwe e n o n e to

f

iv e _ye a r s ol d.

C h i l d

r e n

a

_g

e

d

o n e to two _ye a r s

h

a

d

a _ge o

m

etr

i

c

m

e a n b lo od le ad of

3

. 1_yU g

/

d L

, w ith

5

.

9

pe r c e nt

s uf fe rin_{g f}r o

m

ele v ated b lo o d le ad le v els. C h i l dr e n a

ged 3 to _{5 y}e a r s had a _ge o

m

etric

m

e a n b lo od le ad of 2.5 fxg / d L , w ith 3.5 pe r c e nt s u f fe ring ele v ated b lo od le ad le v e

l

s.

4

.

1

.

1

.1 Be

h

a vio r al F a cto r s

Toda_y t

h

e

m

a

_j

o r

f

a cto r that

l

e a

d

s to e x c e s s a

b

s o r_pt

i

o n of le ad in ch i l dr e n

i

n

c e rtain a r e a s is the a

m

o u n t of r e si de ntial le ad fo u n

d i

n s oi l a nd du st

C h

i

l d

r e n

l

ivin

_g

in

s

m

elte r c o

m

m

u nit

i

e s o

f

te n ha v e a h

i g

he r risk of le a

d p

ois o nin_g. In lo n

g

-te r

m

stu

d i

e s o

f

the s e co

m m

u nit

i

e s,

l

e a

d

a

b

ate

m

e nt

p

r o

g

r a

m

s t

h

at a

i m

to c o ntr ol eithe r o ut

d

o o r

l

e a

d

c o nta

m i

n at

i

o n ,

i

n

d

o o r

l

e a

d

c o nta

m i

n at

i

o n , o r

b

ot

h

,

h

a v e

p

r o v e n to

b

e o n

l

y

m

o

d

e r ate

l y

s u c c e s s

f

u

l i

n

l

owe r

i

n_g c

h i l d

r e n's

b l

o o

d l

e a

d l

e v e

l

s. Be

h

a v

i

o r al fa cto r s in c r e a s e a c

h i l d

'

s u s c e_pti b i l it_y to le ad pois o nin_{g b}e ca u s e of in c r e a s ed e x_po s u r e s to le ad. T h is beha vio r

i

n clude s :

•

p la_{y i}n_{g i}n c o nta

m

in ated a r e a s

₍

_i e., s oi l

)

;

•

m

_{o uth in}

g ite

m

s c o nta

m

in ated w ith le ad fr o

m

_paint, du st, a nd s oi l; a n d

•

p ic a, the te nde n cy to e at n o nfo od ite

m

s, s u ch a s d irt

(

H u nter, 1 9 7 7

)

4.1.1.2 B io

l

og

i

c a

l

F a cto r s

T he

m

e c

h

a n

i

s

m

o

f

a ctiv e tr a n s

_p

o rt d

i

s

_{p l}

a

_y

s a str o n

_g

a_ge

d

e

_p

e n

d

e n c e,

b

e

i

ng

m

o r e

i

_{m p}

o rta nt at _yo u n_ge r a

_g

e s fo r le ad

(

T R

W

, 1 9 9 4

)

. B iolog ic al fa cto r s a r e a s s o ciated w ith a

gr e ate r s e n sitivit_y to the ef fe cts of le ad at the s a

m

e do s e le v els a s adu lts. T he risk fa cto r s

w h

i

c

h

c o n

f

e r a

b

iolo _{g i}c al s u s c e

_p

ti

b

i l it_{y i}n c

h i

l

d

r e n in clu

d

e :

•

the

d

e v e

l

o

_{p i}

n

_g

n e r v o u s s_yste

m

;

•

t

h

e e

f f

icie n c_y of le a

d

a

b

s o r_ptio n in the G I tr a ct ; a n

d

•

n utritio n al defi cie n cie s.

C h i l dr e n abs o rb abo ut hal f of in_ge sted le ad

—

a r ate that is abo u t f iv e ti

m

e s h i g he r

tha n the a

d

u

l

t r ate. Yo u ng ch i l dr e n ofte n show a gr e ate r pr e v ale n c e of n utritio n a

l

def icie n c_y , a c o n

d i

tio n w h ich is kn ow n to in c r e a s e

G

I abs o rptio n o

f l

e ad. T he

G

I syste

m

of a ch i l d r e s

_p

o nds to in c r e a s ed n utritio n al n e eds b y in c r e a sin_g abs o r

_p

tio n of the

pa rtic ula r n u trie nt. T h is is r e s

p

o n si b le fo r the e nha n c ed abs o r