Effects of Lead Levels on Indoor and Built Environment in Ibadan Oyo State, Nigeria

ABSTRACT

Environmental exposure to lead, a highly toxic heavy metal, is a significant cause of human morbidity and mortality. However, the determination of lead levels in homes and built environment have not been well investigated in Nigeria. This study was designed to evaluate the lead levels in dust, paint, paint chips, soil and water; and to ascertain the geotechnical properties of soil in the home environment in Ibadan. Four Focus Group Discussions (FGDs) were conducted and six hundred questionnaires randomly administered to evaluate knowledge about lead exposure in Ibadan. Responses were compared using Wilcoxon rank-sum tests for continuous variables and χ2 for categorical variables at p = 0.05. Lead levels in paint from twenty-five samples obtained from five manufacturers were measured. Three-hundred samples from urban areas were taken randomly from dust from door step of the house entrances and window sills, paint chips from walls, soil at 2000mm from fence wall and 300mm depth from front and back of the houses and portable water from taps and their lead levels measured. Atomic Absorption Spectroscopy was used to determine the lead levels in these samples. Geotechnical engineering tests were carried out to determine the Maximum Dry Density (MDD), Optimum Moisture Content (OMC), Liquid Limit (LL), Plastic Limit (PL), and California Bearing Ratio (CBR) of the sampled soil. Most respondents (86%) from the FGDs and the questionnaires (86%) had no knowledge about lead exposure in home environment. Twenty-four (96%) from the twenty-five paint samples exceeded the recommended lead level in paint of 90 ppm. Yellow paint had the highest lead level of 50,000 ppm; indicating high risk and white paint had the lowest lead level of 84 ppm. Dust lead levels from door steps of house entrances have average of 115.1 ± 1 12.9 ppm and dust lead levels from window sills have average of 83.3 ± 13.3 ppm; due to lack of proper regular cleaning. Paint chips lead levels from walls have average of 2,894.6 ± 79.5 ppm; due to flaking old paint that emits lead. Soil lead levels in front of houses have average of 135.3 ± 4.5 ppm and soil lead levels from back of the houses have average of 69.4 ± 5.9 ppm; due to lack of landscaping to cover exposed soil surfaces. Potable water lead levels have average of 0.21 ± 0.02 ppm, against recommended value of 0.01 ppm due to usage of lead water pipes. The values of the geotechnical parameters obtained ranged from 1.8 – 2.0 g/cm3 (MDD), 8.5 - 13.8% (OMC), 17.8 – 29.6% (LL), 14.2 – 23.4% (PL), and 59 - 95% (CBR); all within normal recommended values.

The indoor and built environments in Ibadan are highly affected by high lead levels. Lead levels in paint used in homes should be reduced to minimize human morbidity and mortality. The usage of non-lead water pipes is highly recommended. Lead levels in soil in the home environment do not affect the geotechnical characteristics of soil.