- Environmental contamination along roadways with lead from processed
petroleum and automotive residues has been reported. Toxicity to the herbivores grazing these areas has not been well studied. Comparison of lead concentrations adjacent to roads in Kuwait and in Oregon, USA was studied. Soil samples were taken from three sites at three different distances from the highway (0, 3 and 10 meters) adjacent to King Fahad Highway in Kuwait and Interstate 5 (I-5), Highway 34 (H-34) and Highway 20 (H-20) in Oregon. Soil was analyzed for lead concentrations. The mean lead concentrations in soil samples along King Fahad Highway were significantly higher (p<0.05) than those
along 1-5, H-34 and 14-20 in Oregon [4943.6 ppm (mg/kg) vs 129 ppm, 94.9 and 81.67
In a field trial animal toxicity studies were conducted on sheep grazing near
roadway in Kuwait and also in a controlled barn studies. Fifty lambs ranging in age from
4 to 9 months and grazing on Kuwait pasture adjacent to the King Fahad Highway were
tested for blood lead. Levels were determined by Inductively Coupled Plasma-Atomic
Emission Spectrometry (ICP-AES). Blood lead levels of these lambs ranged from 0.05-1.00 ppm. Only 12% of the tested population exceeded the blood lead above 0.1 ppm (the
high normal value). None demonstrated any clinical signs of lead toxicosis.
In addition, a controlled feeding trial was conducted with sheep ingesting similar
concentrations of lead as were found along the roadways. These sheep were observed for
clinical, gross and histopathological changes. Using the intensive lamb production system
common in Kuwait, twenty five lambs ranging in age from 2-10 months were orally fed
0, 2, 4, 8 and 16 mg lead acetate/kg body weight/day in a controlled study. Blood lead
levels were tested in these lambs at time zero, week two, and then at monthly intervals
until the 14th week. All lambs were slaughtered and necropsied with select tissues
analyzed for lead concentrations.
Levels of lead in the blood were directly related to the daily administrated lead
acetate (P<0.05). Neither gender, age nor breed of the sire had any affect on blood lead
levels except for the 14th week where blood lead levels of the young lambs significantly
exceeded (P<0.05) those in the older lambs with mean values of 0.54 and 0.34 ppm
respectively. In general, lead levels in all the tested tissues were directly related to the
amount of the daily oral administration of lead acetate. Differences between the tissue
levels of lead in the experimental and control lambs (N=25) were statistically significant
(P<0.05) in liver, bone and kidney but were not significant in trachea, testis, brain,
diaphragm, ovary, lung, muscle, rumen, aorta, spleen, tongue, eye, intestine, heart and
esophagus. Lead accumulation was the highest in bone at the lower ingested lead
concentrations, but was the highest in the kidney at higher lead dosages. Lead values
were significantly greater (P<0.05) in the livers of female lambs compared to those of the
male. Bone, liver and kidney of the young lambs had significantly higher (P<0.05) levels
of lead than older lambs with means of 19.24, 7.31 and 54.54 compared to 6.34, 3.59 and
21.31 ppm respectively. Gross lesions were not found in any of the 25 necropsied lambs.
Histopathological changes of intranuclear inclusion bodies were found in 100% of the
kidneys in lambs administered 8 mg/Kg/day and above and in 50% of the livers of the
lambs administered the same dosages. Thirty three per cent of lambs administered 2 and 4
mg/kg/day had intranuclear inclusion bodies in their kidney but not in the liver. The
controls had no inclusion bodies in any of these matching tissues. No clinical signs of
lead toxicosis were observed in any lambs during the 14 weeks of the experiment.
The same lamb population was used to compare blood lead levels and the growth
performance of lambs (feed intake, weight gain and feed conversion) in relation to
different dosages of lead acetate. Although there was a tendency for lambs ingesting the
two higher lead doses to eat less feed, gain less weight; and have a lower feed conversion
ratio, these differences were not statistically significant (P>0.05).
The conclusion of these studies reveal some concern. Levels of lead as found near
the highways of Kuwait were high enough to cause elevated tissue lead concentrations,
particularly in liver and kidney, of lambs grazing adjacent to these highways. These
levels cause tissue abnormalities in lambs and could be hazardous to human health eating
the internal organs of these lambs.