Urinary dialkyl phosphate levels before and after first season chlorpyrifos spraying amongst farm workers in the Western Cape, South Africa.

The study investigated urinary levels of dialkyl phosphates resulting from pesticide exposure amongst 40 farm workers. Workers were tested (urinary dialkyl phosphate levels, anthropometry, short exposure questionnaire) before and after the first day of seasonal chlorpyrifos spraying. Median baseline urinary dialkyl phosphates was high amongst both non-applicators (1587.5 µg/g creatinine, n = 8) and applicators (365.6 µg/g creatinine, n = 9). There was not much evidence of an increase in post-spray dialkyl phosphates levels from pre-spray levels amongst both applicators and non-applicators. Hours mixing, spraying, driving a tractor and hours worked by non-applicators were not significantly associated with an increase in post-spray dialkyl phosphate levels, adjusting for age, height, weight, gender, use of empty pesticide containers and self-reported kidney problems. Past applicator status was weakly positively associated with pre-spray dialkyl phosphate levels adjusting for age, height, weight, and gender, self-reported kidney problems, smoking and alcohol (ß= 1019.5, p = 0.307, R² = 0.28). The high dialkyl phosphate levels call for an epidemiological investigation into the health effects of organophosphorous pesticides.

A trace metal survey of non-occupationally exposed Gauteng residents.

Specific reference values for background levels of body burden of trace metals are not available for South Africa. Currently, laboratories measuring trace metal levels in workers use internationaly established values for comparison. A preliminary cross-sectional survey of 107 non-occupationally exposed volunteers of both genders and all races provided blood and urine samples. The samples were collected with consideration for possible routes of contamination. Seven metals were measured in blood and ten in urine. Reference ranges for a Gauteng population were then calculated using the central 95% of data to provide lower and upper limits, which were then compared to international limits. The trace metal levels described had both lower and higher reference ranges in blood and urine compared to international studies. This reflects the differences in the environments. Statistically significant differences in metal levels were observed by gender. The differences in detected trace metal levels in our sample as compared to other published data demonstrate the need for the establishment of local reference values for laboratories. The establishment of local 95% reference ranges would also allow South Africa to determine its exposure levels compared to those internationally. This would assist with establishing pollution control priorities.

Examining the association between blood manganese and lead levels in schoolchildren in four selected regions of South Africa.

This study assessed the possibility of relationship between manganese and lead levels in blood in schoolchildren residing in different geographical regions of South Africa. A cross-sectional survey was carried out in schools of three cities: Cape Town (11 schools), Johannesburg (10 schools), Kimberley (six schools) and in the Northern Cape in three rural sites (four schools). A total of 1282 venous blood samples were collected from grade one children. The relationships between blood manganese and blood lead levels (treating each in turn as the response variable in order to adjust for the effect of confounding variables) were investigated by fitting mixed models. Mixed models were fitted with natural log (manganese concentration) as the response variable, and blood lead level as the principal explanatory factor. The model also included terms for centre and a centre by lead interaction and examined potential confounders. The important confounders were found to be gender, race and whether there was paint peeling from the outside walls. There was a significant centre by lead interaction (P<0.0001) with the effect of lead on ln(Mn) being different in the various centres. Mixed models fitted with blood lead level as the response variable and blood manganese as the principal explanatory factor, with terms for centre, a centre by manganese interaction and potential confounders, again found overwhelming evidence (P<0.0001) of a centre by manganese interaction. The study found great variability in both blood lead and manganese levels, both within and between sites, and there was not a consistent relationship between the two metals in the four sites.

Reductions in blood lead levels among school children following the introduction of unleaded petrol in South Africa.

Epidemiological studies have indicated that in the 1980s and early 1990s (a period in which petrol lead concentrations in South Africa ranged from 0.836 to 0.4 g/L), large proportions of urban South African children were at risk of excessive exposure to environmental lead. In 1991, when the maximum permissible petrol lead concentration in the country equaled 0.4 g/L, a study determined that the mean blood lead level among children attending inner city schools in the Cape Peninsula equaled 16 microg/dL, with well over 90% of children having blood lead levels equaling or exceeding the internationally accepted guideline level of 10 microg/dL. Socio economic status, housing conditions, and proximity of children's schools and homes to heavily trafficked roads were among the factors significantly associated with blood lead concentrations. In 1996, unleaded petrol was introduced in South Africa. A study undertaken in 2002 (at the same schools as in 1991), when unleaded petrol constituted around 30% of the market share of petrol in the country, has shown significant reductions in the mean blood lead concentration among Cape Peninsula inner city children and in the proportion of children with elevated blood lead levels. The mean blood lead level for the total sample (n = 429) of children whose mean age equaled 7 years (range: 5-11 years) was 6.4 microg/dL (range: 1.0-24.5 microg/dL) and 10% of children had blood lead levels equalling or exceeding 10 microg/dL. The mean blood lead levels among children attending schools in an inner city and in a less heavily trafficked periurban suburb were 6.9 and 4.8 microg/dL, respectively.