Table 3.
Summary of the results of the literature review of the combined effects of noise and chemical agents
| Chemical agents | The level of combined risk | Level of evidence | Effects | Comments | Study | |
|---|---|---|---|---|---|---|
| Quantitative | Qualitative | |||||
| Noise & CO | Exposure to Leq > 80dBA and CO concentration > 200 ppm | Additive | High | Hearing loss, fatigue, impaired cognitive performance, | The CO induces cochlear hypoxia,in result, aggravate NIHL | [74], [75], [76], [77], [78], [79], [80], and [81] |
| Noise & solvents | Exposure to Leq > 80 dBA and concentrations equal to 50–300 ppm | Synergistic | High | hypertension | Styrene, toluene, hexane, xylene, acetone, butanol, trichloroethylene, and ethanol have combined effects with noise | [82], [83], [84], [85], [86], [87], [88], [89], [90], [91], [92], [93], [94], [95], [96], [97], [98], and [99]. |
| Noise & heavy metals | Exposure to Leq = 80–95dBA and lead (Pb = 0.05 mg/m3), (manganese = 10 mg MnCl2/liter water), cadmium (2 mg/kg) | Synergistic | High | Hearing loss | Lead, mercury, arsenic, cadmium have combined effects with noise | [100], [101], [102], [103], [104], [105], [106], [107], [108], [109], [110], [111], [112], and [113] |
| Noise & other chemical | Exposure to Leq > 80 dBA | Additive | Medium | Hearing loss | Epoxy adhesives and organophosphate pesticides have combined effects with noise | [114], [115], and [116] |
Level of evidence: was determined based on the number of citations, methodological quality and design, validity, and applicability of studies results (Low − Medium − High). The Level of combined risk: The degree of effect intensification caused by the simultaneous presence of two factors or agents that was determined based on the design and study type, the methodological, validity of data, and the study population. Additive effect: The combined effect produced by the action of two or more agents, being equal to the sum of their separate effects (2+2=4). Synergistic effects: An effect arising between two or more agents, or factors, that produces an effect greater than the sum of their individual effects (2 + 2 = 25). Potentiation effects: The combination of a factor or agent that has no effect (0) with a factor or agent that has some effect (2) is equal to the combined effect (10) greater than the sum of the effects of each one alone (0 + 2 = 10). Antagonism effect: Two or more combined agents have an overall effect that is less than the sum of their individual effects (5 + 0 = 2).