The relationship between lead levels and reading acquisition in Spanish speakers, evidence from Uruguayan schoolers

Lead is a well-known neurotoxicant that continues to affect children´s cognition and behavior. Nevertheless, we still have little evidence on the consequences of lead exposure on reading abilities, particularly in languages other than English.

To investigate the cross-sectional association between blood lead levels (BLL), and pre-reading and reading abilities in first-grade children from Montevideo, Uruguay.

Of 357 school children (age 67-105 months) enrolled into the study, 287(43 % girls) had a BLL measure and an assessment of pre-reading and reading abilities based on five tests (Verbal comprehension, Sound blending, Letter word identification, Sentence reading fluency, and Passage comprehension) from the Batería III Woodcock-Muñoz. Separate generalized linear models (GLM) were conducted on the relationship between BLL and each test score separately, adjusting for sex, maternal education, household assets, Home Observation for Measurement of the Environment Inventory score, season, test administrator, blood lead testing method, and school clusters.

The mean BLL was 4.0 ± 2.2 µg/dL, with no differences between the sexes. BLL was associated with a poorer vocabulary knowledge (β [95 % CI]): -0.20 [-0.39, 0.01]. For all the tests, children with BLLs ≥5 µg/dL tended to exhibit poorer performance than children with lower BLLs, but these associations were not statistically significant. When stratified by sex, some evidence of differential associations between BLLs and reading abilities emerged: BLLs were associated with higher phonological awareness in girls (0.32 [0.15, 0.48]) but not boys, and with lower reading comprehension in boys (-0.54 [-1.20, 0.13]) but not girls. Also, lead exposure (BLL ≥ 5 µg/dL) was more strongly and negatively associated with phonological awareness (-1.22 [-1.57, -0.86]) in boys than girls.

In this study of first-grade children learning to read in Spanish, we found an inverse association between lead exposure and vocabulary scores, as well as tendency toward lower performance on pre-reading and reading measures among children with BLLs ≥5 µg/dL. Pre-reading and reading abilities are relevant to literacy acquisition; further research is required to confirm these links in larger studies, and to investigate differences between boys and girls, and according to key sociodemographic characteristics.