Black carbon particles in human breast milk: assessing infant's exposure

Abstract

Background/aim: Human breast milk is the recommended source of nutrition for infants due to its complex composition and numerous benefits, including a decline in infection rates in childhood and a lower risk of obesity. Hence, it is crucial that environmental pollutants in human breast milk are minimized. Exposure to black carbon (BC) particles has adverse effects on health; therefore, this pilot study investigates the presence of these particles in human breast milk.

Methods: BC particles from ambient exposure were measured in eight human breast milk samples using a white light generation under femtosecond illumination. The carbonaceous nature of the particles was confirmed with BC fingerprinting. Ambient air pollution exposures (PM_2.5, PM₁₀, and NO₂) were estimated using a spatial interpolation model based on the maternal residential address. Spearman rank correlation coefficients were obtained to assess the association between human breast milk's BC load and ambient air pollution exposure.

Results: BC particles were found in all human breast milk samples. BC loads in human breast milk were strongly and positively correlated with recent (i.e., 1 week) maternal residential NO₂ (r = 0.79; p = 0.02) exposure and medium-term (i.e., 1 month) PM_2.5 (r = 0.83; p = 0.02) and PM₁₀ (r = 0.93; p = 0.002) exposure.

Conclusion: For the first time, we showed the presence of BC particles in human breast milk and found a robust association with ambient air pollution concentrations. Our findings present a pioneering insight into a novel pathway through which combustion-derived air pollution particles can permeate the delicate system of infants.

Keywords: air pollution; black carbon; human breast milk; infants; public health.

Figure 1

Evidence of BC particles in human breast milk. (A) Emission fingerprinting in human breast milk of BC particles, reference particles (CCB), and two-photon autofluorescence (TRAF) under femtosecond-pulsed illumination. (B) Localization of BC particles in human breast milk. Autofluorescence of human breast milk is given in magenta, and BC particles are shown in white (indicated by the white arrowhead). Scale bar: 20 μm.

Figure 2

Correlation between BC load in human breast milk and maternal residential air pollution exposures 1 week before sampling (i.e., recent) or 1 month before sampling (i.e., medium-term). Spearman’s correlation coefficients were obtained for all exposures. The solid lines indicate the regression lines with the 95% CIs (grey areas).