Background
On a daily basis, workers in a wide range of industries come in contact with a harmful metal called lead. There is no known level of exposure to lead that does not cause harm to health, therefore, reducing exposure is essential. Educational programmes and training can prevent the uptake of lead in workers.
What is the aim of this review?
We searched five databases for randomised (RCT) and non-randomised studies to assess the effectiveness of these educational programmes.
Key messages
Educational interventions may prevent lead poisoning in workers but we are very uncertain of this finding , therefore, more studies of better quality are required.
What was studied in the review?
We included four uncontrolled before-after studies in this review. The studies assessed the effectiveness of educational interventions for preventing lead uptake in workers exposed to lead. We assessed a critical risk of bias in three studies and a moderate risk of bias in one.
What are the main results of the review?
Very low-quality evidence from three studies with participants with high baseline blood lead levels, suggested a decrease in blood lead after education; one study with participants with low baseline blood lead found conflicting results. Very low-quality evidence from one study suggested a decrease in urinary lead levels.
There may be an effect, but we are very uncertain if educational interventions are effective in preventing lead poisoning in workers with high baseline blood lead levels and urine lead levels. For workers with low baseline blood lead levels, the results were inconclusive.
How up-to-date is this review?
We searched for studies to 5 June 2020.
Educational interventions may prevent lead poisoning in workers with high baseline blood lead levels and urine lead levels but this is uncertain. Educational interventions may not prevent lead poisoning in workers with low baseline blood lead levels but this is uncertain.
Occupational lead exposure can lead to serious health effects that range from general symptoms (depression, generalised ache, and digestive signs, such as loss of appetite, stomach ache, nausea, diarrhoea, and constipation) to chronic conditions (cerebrovascular and cardiovascular diseases, cognitive impairment, kidney disease, cancers, and infertility). Educational interventions may contribute to the prevention of lead uptake in workers exposed to lead, and it is important to assess their effectiveness.
To assess the effect of educational interventions for preventing lead uptake in workers exposed to lead.
We searched CENTRAL, MEDLINE, Embase, CINAHL, and OSH UPDATE to 5 June 2020, with no language restrictions.
We sought randomised controlled trials (RCT), cluster-RCTs (cRCT), interrupted time series (ITS), controlled before-after studies (CBA) and uncontrolled before-after studies that examined the effects of an educational intervention aimed at preventing lead exposure and poisoning in workers who worked with lead, for which effectiveness was measured by lead levels in blood and urine, blood zinc protoporphyrin levels and urine aminolevulinic acid levels.
Two review authors independently screened the search results, assessed studies for eligibility, and extracted data using standard Cochrane methods. We used the ROBINS-I tool to assess the risk of bias, and GRADE methodology to assess the certainty of the evidence.
We did not find any RCT, cRCT, ITS or CBA studies that met our criteria. We included four uncontrolled before-after studies studies, conducted between 1982 and 2004.
Blood lead levels
Educational interventions may reduce blood lead levels, but the evidence is very uncertain. In the short-term after the educational intervention, blood lead levels may decrease (mean difference (MD) 9.17 µg/dL, 95% confidence interval (CI) 4.14 to 14.20; one study with high baseline blood lead level, 18 participants; very low-certainty evidence).
In the medium-term, blood lead levels may decrease (MD 3.80 µg/dL, 95% CI 1.48 to 6.12; one study with high baseline blood lead level, 34 participants; very low-certainty evidence).
In the long-term, blood lead levels may decrease when the baseline blood lead levels are high (MD 8.08 µg/dL; 95% CI 3.67 to 12.49; two studies, 69 participants; very low-certainty evidence), but not when the baseline blood lead levels are low (MD 1.10 µg/dL, 95% CI -0.11 to 2.31; one study, 52 participants, very low-certainty evidence).
Urine lead levels
In the long-term, urinary lead levels may decrease after the educational intervention, but the evidence is very uncertain (MD 42.43 µg/L, 95% CI 29.73 to 55.13; one study, 35 participants; very low-certainty evidence).
Behaviour change
The evidence is very uncertain about the effect of educational intervention on behaviour change. At medium-term follow-up after the educational intervention, very low-certainty evidence from one study (89 participants) found inconclusive results for washing before eating (risk ratio (RR) 1.71, 95% CI 0.42 to 6.91), washing before drinking (RR 1.37, 95% CI 0.61 to 3.06), and not smoking in the work area (RR 1.04, 95% CI 0.74 to 1.46). Very low-certainty evidence from one study (21 participants) suggested that employers may improve the provision of fit testing for all respirator users (RR 1.87, 95% CI 1.16 to 3.01), and prohibit eating, drinking, smoking, and other tobacco use in the work area (RR 4.25, 95% CI 1.72 to 10.51), however, the results were inconclusive for the adequate provision of protective clothing (RR 1.40, 95% CI 0.82 to 2.40).
At long-term follow-up, very low-certainty evidence from one study (89 participants) suggested that workers may improve washing before drinking (RR 3.24, 95% CI 1.09 to 9.61), but results were inconclusive for washing before eating (RR 11.71, 95% CI 0.66 to 208.33), and for not smoking in the work area (RR 1.56, 95% CI 0.98 to 2.50). Very low-certainty evidence from one study (21 participants) suggested that employers may improve the provision of fit testing for all respirator users (RR 1.70, 95% CI 1.09 to 2.63), may provide adequate protective clothing (RR 2.80, 95% CI 1.23 to 6.37), and may prohibit eating, drinking, smoking, and other tobacco use in the work area (RR 2.13, 95% CI 1.19 to 3.81).
Improved knowledge or awareness of the adverse health effects of lead
The evidence is very uncertain about the effect of educational intervention on workers' knowledge. At medium-term follow-up, questionnaires found that workers' knowledge may improve (MD 5.20, 95% CI 3.29 to 7.11; one study, 34 participants; very low-certainty evidence).
At long-term follow-up, there may be an improvement in workers' knowledge (MD 5.80, 95% CI 3.89 to 7.71; one study, 34 participants; very low-certainty evidence), but results were inconclusive for employers' knowledge (RR 1.67, 95% CI 0.74 to 3.75; one study, 21 participants; very low-certainty evidence).
None of the studies measured the other outcomes of interest: blood zinc protoporphyrin levels, urine aminolevulinic acid levels, air lead levels, and harms. One study provided the costs of each component of the intervention.