A research paper on residue of pesticides in human milk.Levels of residues of chlorinated hydrocarbons p,p-DDT, p,p-DDE, p,p-TDE, x-, B-, y-hexachlorocyclohexane (HCH), heptachlor epoxide, dieldrin and polychlorinated biphenyls (PCBs) in the milk of 40 Zimbabwean mothers living in the Greater Harare area were analysed. Of all the milk samples analysed, relatively low residue levels of x-, B-, and v-HCH, peptochloroperoxide and dieldrin were detected in 58, 100, 63, 13 (not statistically significant) and 65 per cent respectively. Traces of the PCB congener 2,2,4,5,5 -penta- chlobipheny (PCB 101) were found in 15 samples. One sample contained traces of 2,3',4,4',5-pentachlorobiphenyl (PCB 118). From this study, small though the sample was, it seems social status, educational background and living conditions are important demographic variables influencing the frequency distribution of residue levels of sum DDT in the mother’s milk

Chikuni, Ordias

Nhachi, Charles F.B.

English

IDS OpenDocs

Edited by
Charles F. B. Nhachi 
and
Ossy M. J. Kasilo
PESTICIDES IN ZIMBABWE
Toxicity and Health Implications
Edited by
C h arles  F. B . N h a ch i 
an d
O ssy  M . J. K a s ilo
University of Zimbabwe Publications 
Harare
Chapter 8
Residues of organochlorine pesticides in human milk. 
O r d ia s  C h i k u n i  a n d  C h a r le s  F . B . N l i a c h i 73
Chapter 9
Occupational exposure to DDT am ong the mosquito-control 
sprayers in Zimbabwe.
C h a r le s  F . B .  N l i a c h i ,  W i lb e r t  M u r a m h iw a ,
R o s e m a r y  U r o r n b o  a n d  O s s v  M .  J. K a s i l o  81
Chapter 10
Organochlorine pesticide residues in inland w;aters in Zimbabwe.
M a r k  F . Z a r a n y ik a  a n d  J o h n  M .  M a k h u h a lo  89
Sum m ary 89
Introduction 89
The aquatic environment in Zim babwe 89
Evidence of pestcicde residue build-up in, lakes 91
Pollution from tsetse- and malaria-control sprays 98
Conclusion 106
Acknowledgements 106
References 106
Chapter 11
Metabolism of pesticides.
O s s y  M .  J. K a s i l o  a n d  C h a r le s  F . B . N l i a c h i  107
Chapter 12
M anagement of pesticide poisoning.
C h a r le s  F . B . N l i a c h i  a n d  O s s y  M .  J. K a s i l o  111
Sum m ary 111
Introduction 111
M anagement of pesticides 112
Organophosphates and carbamates 112
Organocholines 113
Herbicides 113
Pvrethroids 114
References 115
8
Residues of Organochlorine 
Pesticides in Human Milk
Ordias Chikuni and Charles F. B. Nhachi
Summary
Levels of residues of chlorinated hydrocarbons p,p-DDT, p,p-DDE, p,p-TDE, x-, 
B-, y-hexachlorocyclohexane (HCH), heptachlor epoxide, dieldrin and 
polychlorinated biphenyls (PCBs) in the milk of 40 Zimbabwean mothers 
living in the Greater Harare area were analysed. Of all the milk samples 
analysed, relatively low residue levels of x-, B-, and v-HCH, peptochloroperoxide 
and dieldrin were detected in 58, 100, 63, 13 (not statistically significant) and 
65 per cent respectively. Traces of the PCB congener 2,2,4,5,5 -penta- 
chlobipheny (PCB 101) were found in 15 samples. One sample contained 
traces of 2,3',4,4',5-pentachlorobiphenyl (PCB 118). From this study, small 
though the sample was, it seems social status, educational background and 
living conditions are important demographic variables influencing the frequency 
distribution of residue levels of sum DDT in the mother’s milk.
DDT, Dichlorodiphenvl trichloroethane, has been in use in Zimbabwe for four 
and half decades, from 1946 to 1982. DDT was registered in Zimbabwe for 
both public health and agricultural use such as the control of A n o p h e le s  
mosquito and tsetse fly, vectors of malaria and sleeping sickness/Nagana 
respectively, agricultural pests such as maize stalkborer ( B u s s e o la  f u s c a ) ,  cotton 
cutworm ( A g r o t is  s p p ) ,  and cotton boll worm (H e l io t h i s  s p p ) .  There is also 
evidence that DDT has been used as an insecticide to control pests of stored 
grain since 1982. DDT is registered by the Ministry of Health’s Hazardous 
Substances Control Board as a “hazardous substance class 1”, that is, a 
chemical that can endanger humans, domestic and wild animals and its 
procurement and use is restricted to cover tsetse and mosquito control only.
Environmental contamination by DDT in Zimbabwe is, therefore, related to 
its use as a vector control agent. DDT could find its way into the human body 
when inhaled as house dust, after the houses have been sprayed with DDT 
during the mosquito control exercise. However, the major source of DDT 
intake in the general population, accounting for over 90 per cent of individuals 
positive lor DDT in blood or lat, is food.
Studies have been carried out in Zimbabwe to assess pesticide residue levels 
in serum (Mpofu, 1986). Since the first report of the presence of DDT in
74 PESTICIDES IN ZIMBABWE
human milk in 1951 by Laugh ct al.. n number <>l'studies have been carried to 
assess the presence of DDT residues in human milk (Jensen, 1983). Bouwman 
vl al. (1990) determined the concentrations ol DDT and its metabolites DDE 
and DDI) in the breast milk of KwaZulu (South Africa) mothers. It was found 
that DDT and DDK in breast milk increased alter the application of DDT.
In Zimbabwe, Chikuni vl al. (1991) published results of a survey and analysis 
o f “Residues of organichlorinc pesticides in human milk from mothers living 
in the Greater Harare citv of Zimbabwe . This chapter is based on discussion 
and conclusions ol the results Irom that study.
Mothers who had lived in four ol the high or low densitv suburbs, around 
the capital lor more than live rears were randomly selected and enrolled into 
the study. The lour high densitv suburbs selected are Mbare, Epworth, 
Mulakose-Kambit/,uma and Dzivaresekwa and the low density suburbs are 
Milton Park, Queensdale, Avondale and Borrowdale. A total ol 40 healthy 
breasl-leeding mothers were interviewed using a pre-tested questionnaire and 
provided breast milk samples lor analysis. The average age and parity ol the 
mothers were 35 vears and 1-3 respectively.
Milk samples were collected by means ol manual expression. The samples 
( 10 ml) were preserved w ith 50 ml ol 33 per cent formalin, taking special care 
to avoid contamination. All samples were stored at 10nC until analysis. The 
milk samples were homogenized with an Ultrasonic homogeniser. Extraction, 
clean up and analvsis ol samples were carried out according to the modified 
method of Brevik (1978). PCBs were determined using gas chromatography 
against individual PCB isomers. The data obtained was evaluated lor 
signilieance ( P< 0,05) bv the Wilcovan’s two-sample test ( I lodges and l.ehcmann. 
1970).
Milk-supplying mothers were classilied into two groups according to socio­
economic status, educational background and living conditions. Group 1 
mothers (14) lived in the low densitv suburbs and bad a relatively high socio­
economic status and dietary habits, a good knowledge ol pesticides and their 
use. Group 2 mothers (26) lived in the high densitv suburbs anti had a t elalivelv 
low socio-economic status, a basic educational background, poor dietary habits 
and bad poor knowledge ol pesticides and their use.
The statistical data is expressed on a I at weight basis as arithmetic mean 
together with range for the single determination o f each of the samples. 
Median values are also given lor sum DDT and DDT/DDH ratios (see Table I ).
The results are expressed as means. The ranges are listed in parentheses. 
There were no signilicant ditlerences between corresponding results Irom the 
two groups, w hen p > 0,05. Group II mothers showed high mean levels of sum 
DDT compared to that ol Group I mothers. The highest indiv idual sum DDT in 
Group II was six times higher than that o f Group I. The ratio DDT/DDH was 
higher in Group II mothers. The main organochlorine contaminants lomul in 
all the 40 samples were p.p’-DDT anti the mote persistent metabolites, p.p'- 
TDK and o.p'-DD T.
Residues of organochlorine pesticides in human milk 75
Tabic 1: Residues (ppm. mg per kg fat weight) of sum DDT and the ratio 
DDT/DDE in Zimbabwe human milk.
Group Sum ol DDT DDT/DDE
Mean Median Mean Median
Group 1 
R 11
5,00
(0,59 -55,50)
3,22
(0,59-55,5.3)
0,74
(0,06-6,40)
0,36
(0,00-6,44)
Group 1 3,44
(0,63-8,31)
3,10
(0,6.3-8,31 )
0,37
(0,00-1,05)
0,21
(0,00 1.05)
Group I] 7,39
(0,59 55,50)
3,97
(0,59-55,53)
0,93
(0,1 1-6,44)
0,45
(0,1 1-6.44)
Table 2: Residues (ppm, mg per k 
p.p -DDE in human milk
g lal weight ol (p. p ' - T D E . o, p -DDT at
GROIP B A T T D K o . p - D D T p.p '-DlVf p.p -DDE
II & II 3,0 0,43 0,34s 2,39 2,5.3
(0,3-7,71 (0,00-10,67) (0,00-3,83) (0,00-38,16) (0,40 -9,01)
40/40 24/40 39/40 40/40 40/40
1 2,6 0,04 0,1 1 0,90 2,18
(0,74-4,20) (0,00-0.1 5) (0,00-0,41 ) (0.00-3.98) 0.52-5.00)
14/14 5/14 13/14 13/14 14/14
II 3,3 0,64 0,47 3,19 2,71
(0,3-7,7) (0,00-1,67) 0.00-3.83) 0,12 -38.16) 0.40-9.01 )
26/26 1 9/26 25/26 26/26 26/26
Residues of the most persistent metabolite, p,p DDE were observed in all 
the samples and group II mothers Intel the highest level of contamination ol 
this metabolite.
fable 3 below shows mean residue level (in ppm. me per kg ol lal weight) 
ol other' organochlorine pesticides such as x-, B-. \-he\achloiocvclohexanc 
(HCH), heplachlorepoxide and dieldrin observed in the two groups. The table 
shows that the mean levels of the organochlorine pesticides was generally very 
low' compared to that ol the oilier contaminates, that is, DDT and its metabolites 
analvsed. The highest mean level ol the pesticide observed in this table was B 
IICI1 in Group I mother's. In general, a great variation among individual 
samples of the level of contamination was observed.
76 PESTICIDES IN ZIMBABWE
Table 3: Residues (ppm, mg per kg fat weight) ol x-HCH, B-HCH (lit idane
heptachlor epoxide andl dieldrin
Group x HCH B-HCH V-1IC1I I leplachorepox ide DieldIrin
1 & II 0,03 0,84 0,04 0,01 0,08
(0,00-0,16) (0,00-2,63) (0,00-0,49) (0,00-0.07) (0,00--0,82)
23/40 40/40 28/40 8/40 26/40
1 0,04 1,23 0,05 0,00 0,04
(0,00-0,16) 0,34-2,88) (0,00-0,49) - (0,00-0,24)
10/14 14/14 8/14 0/14 7/14
II 0,02 0,62 0,03 0,0! 0,06
(0,00-0,08) (0,00-2,63) (0,00-0,26) (0,00-0,07) (0,00-0,82)
12/26 28/26 16/26 8/26 18/26
Table 4 shows that Zimbabwe has one of the highest DDT/DDE ratios 
compared to all the other countries. More than two times higher mean sum 
DDT 1 evels and 2,6 times higher mean DDT/DDE ratio were found in samples 
from Group II. II owever, the dillerences were not statistically significant. 
Some traces of polychlorinated biphenyls (PCBs) were found in 15 out of the 
40 samples. The isomer identified in all 15 samples was 2,2,4,5, 5 , penta- 
chlorobiphenyl (PCB 101).
The relatively high levels of sum DDT and high DDT/DDE ratio together 
with the presence ol the metabolites p,p'-DDT found in the study analysed 
(Hodges and Lehamann, 1970) reflect a continuing use of DDT as an insecticide 
in agriculture and malaria-control programme in Zimbabwe.
The results of this pilot study suggest that there is a possibility of sustained 
exposure to DDT in the Greater Harare area, particularly in the lower income 
group. Similar results have been lound in Kenya (Kanja e t a l. ,  1986). This has 
serious implications, warranting a country-wide investigation ol the real 
situation. This would help shed light onto whether enough is known about 
pesticide hazard by child-bearing women where pesticides are in general use.
The very low sum DDT levels in the Norwegian study are due to the fact that 
use of DDT is banned in Norway (Jensen, 1987). DDT is still used in India and 
China, hence the high levels that have been reported (Slorach and Vaz, 1983; 
Wamic.x e l a l., 1983; Skaaree/ a l., 1988 and Clench-Ass e t a i ,  1988). The results 
also show that the y-isomers were found in 58 per cent of the milk samples. 
The different isomers have quite different biological properties, the B-isomer 
being the most persistent with the highest accumulation potential (Heechcn, 
1980; Szokalay e t a l. ,  1977). The x- and v-isomers may also isomerise into the 
B-isomer in living organisms (Chikuni e t a l. ,  1991). The ratio between the 
different HCH isomer residues, therefore, may change Irom the start of food
Residues of organochlorine pesticides in human milk 77
Table 4: Residues of organoehlorine pesticides in human milk A comparison 
of mean sum DDT residues (ppm, mg per kg fat weight) and DDT/ 
DDE ratio in human milk from Zimbabwe and some other countries.
Country
Number of
mothers
studied
Fat (%) Sum DDT DDT/DDE Reference
Zimbabwe, 1989 40 3,1 5,91 0,8 5
Kenya, 1983-85 .302 3,2-5,1 1,69-18,73 0,7-5,7 10
China, 1982 100 4,4 6,71 0,4 9
India, 1983
Im migrants 
To Norway 
From Pakistan
50 4,8 6,55 0,3 9
1981-82 7 3,00 5,98 - -
Rwanda, 1983 75 3,3 4,16 0,7 17
Nigeria, 1987 44 2,8 3,83 0,6 8
Norway, 1981-82 36 2,6 0,91 - 13
Norway, 1986 28 3,7 0,58 - 7
chains until excretion in human milk fat, resulting in the more persistent 
isomer being the predominant in human milk as shown in the results (S/.okalay
et a i ,  1977; FAO/WHO, 1978).
The extent of aldrin and dieldrin use in Zimbabwe is probably much less 
than the use of DDT, since only low levels of dieldrin were found in a smaller 
number of samples analysed, l.ow levels of heptachlor epoxide were found in 
only live samples in the present study as compared to what has been reported 
from other countries (Jensen, 1987). Heptachlor, heptachlor epoxide and 
chlordane are closely related chlorinated insecticides. Heptachlor epoxide and 
oxychloradane are very persistent epoxy metabolites of heptachlor and 
chloradane. Traces ol polychlorinated biphenyls, which are major contaminants 
in industrialised countries were found in some breast-milk samples.
The implications of all this to clinical paediatric toxicology is somewhat 
difficult to interpret. If the acceptable daily intake (ADI) for adults estimated 
by the FAO/WHO to be 5 kg per day for sum DDT (Atuma and Okor, 1987) is 
applied, the average infant body w'eight set at 5 kg, the mean intake of milk set
78 PESTICIDES IN ZIMBABWE
at 800 g per day, and the milk assumed to contain 3 per cent w/w lat, a 
“tolerable” concentration of sum DDT in human milk would be 1 mg per kg.
The study by Chikuni e t a l. (1991) indicated that the intake of sum DDT is 
exceeded by several folds by most children. However, there is no evidence so 
far that this has a deleterious effect on the health of the infant. Consequently, 
because of the well-established advantages of breast feeding, this practice 
should still be encouraged. However, a countrv-wide and more extensive study 
of pesticide residues still needs to be carried out.
List ol abbreviations and meanings of compounds mentioned in the text
p,p'-DDT
DDD 
p,p'-DDE 
p,p'-TDE 
IICH 
B-HCH
PCBs 
PCB 101 
PCB 118
L, 1 ,1 -trichoro-2,2-bis (p-chloro-phenyl)  ethane or 
Dichloro-diphenyl trichloroelhane.
Dichloro-diphenyl dichloroelhane
1,1 Dichloro-2,2-bis diphenyl ethylene
Trichloro-diphenyl ethylene
x-, B-, v-hexachlorocyclohexane
Bela benzene hexachloride or gamma-HCH: or
lx, 2x, 3B, 4x, 5x, 6B - hexachlorocyclohexane
Polychlorinated biphenyls
2,2,4,5,5'-pentachlorobiphenyl.
2,3 ,4,4 ,5-pentachlorobiphenyI
Acknowledgements
Thanks to S. Haugen and E. Stai for their technical assistance. Thanks too, to 
the Health Council of the City of Harare for the permission to collect mothers’ 
milk samples in their clinics. Thanks to Dr. J.U. Skaare, Prof. N. Nyazema and 
Dr. A. Polder and to the C e n t r a l A f r ic a n  J o u r n a l  o f  M e d ic in e  for permission to 
publish some of the information in this chapter.
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80 PESTICIDES IN ZIMBABWE
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Residues of organochlorine pesticides in human milk

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Residues of organochlorine pesticides in human milk

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