Department of Chemistry, Oklahoma State University, Stillwater, OK 74078, USA.
Environ Sci Process Impacts. 2022 Jun 22;24(6):973-981. doi: 10.1039/d1em00478f.
Azo dyes are the most common colorants in consumer products, including clothing and cosmetics. Some azo dyes and their products from reductive degradation are known to be mutagenic, so dermal exposure to these species has been studied extensively. In contrast, oxidative degradation of azo dyes in consumer products has not been studied so thoroughly. In the indoor environment, ozone is ubiquitous, so reactive uptake of ozone to azo dyes could lead to dermal exposure to other classes of degradation products. Here, we report the first measurements of the reactive uptake of ozone to thin films of three widely used commercial azo dyes: sunset yellow, amaranth, and tartrazine. Steady-state uptake was observed for all three dyes, under all conditions investigated, even at the lowest relative humidity (RH) of 0%. The uptake coefficients increased with RH. For sunset yellow at 100 ppb of ozone, the value at 80% RH, (2.0 ± 0.5) × 10, was 2.5 times greater than that at 0% RH, (8 ± 1) × 10, consistent with plasticization of the thin film due to absorption of water. The uptake coefficient of sunset yellow at 80% RH exhibited an inverse dependence on the ozone mixing ratio, approaching an asymptote of 1 × 10 above 250 ppb. At 80% RH and 100 ppb of ozone, the uptake coefficients for the three dyes were similar, (2.0 ± 0.5) × 10 for sunset yellow, (2.7 ± 0.6) × 10 for amaranth, and (3.2 ± 0.3) × 10 for tartrazine, despite differences in structural parameters related to the number of reactive sites at the surface. Together, these results are consistent with ozone diffusing into the thin film and the dye molecules mixing between the layers, such that reaction is not restricted to the surface of the film. Finally, the results are suggestive of a role for azo dyes, including the occurrence of their oxidation products, in indoor chemistry.
偶氮染料是消费产品中最常见的着色剂，包括服装和化妆品。已知一些偶氮染料及其还原降解产物具有致突变性，因此人们广泛研究了这些物质的皮肤暴露情况。相比之下，偶氮染料在消费产品中的氧化降解尚未得到如此彻底的研究。在室内环境中，臭氧无处不在，因此臭氧对偶氮染料的反应性吸收可能会导致皮肤接触到其他类别的降解产物。在这里，我们报告了首次测量三种广泛使用的商业偶氮染料（日落黄、苋菜红和柠檬黄）的薄膜对臭氧的反应性吸收。在所有研究的条件下，甚至在相对湿度（RH）最低为 0%的情况下，都观察到了所有三种染料的稳态吸收。吸收系数随 RH 增加而增加。对于在 100 ppb 臭氧浓度下的日落黄，在 80% RH 时的吸收系数（2.0 ± 0.5）× 10 比在 0% RH 时的吸收系数（8 ± 1）× 10 大 2.5 倍，这与由于薄膜吸收水而导致的薄膜增塑作用一致。日落黄在 80% RH 时的吸收系数与臭氧混合比呈反比关系，在 250 ppb 以上时接近 1 × 10 的渐近值。在 80% RH 和 100 ppb 臭氧浓度下，三种染料的吸收系数相似，日落黄为（2.0 ± 0.5）× 10，苋菜红为（2.7 ± 0.6）× 10，柠檬黄为（3.2 ± 0.3）× 10，尽管与表面反应性位点数量有关的结构参数存在差异。这些结果表明，臭氧扩散进入薄膜，染料分子在层间混合，从而使反应不受薄膜表面的限制。最后，结果表明偶氮染料（包括其氧化产物的出现）可能在室内化学中发挥作用。
