Construction noise decreases reproductive efficiency in mice

Abstract

Excessive noise is well known to impair rodent health. To better understand the effect of construction noise and to establish effective noise limits during a planned expansion of our vivarium, we analyzed the effects of construction noise on mouse gestation and neonatal growth. Our hypothesis was that high levels of construction noise would reduce the number of live births and retard neonatal growth. Female Swiss Webster mice were individually implanted with 15 B6CBAF1/J embryos and then exposed to 70- and 90-dBA concrete saw cutting noise samples at defined time points during gestation. In addition, groups of mice with litters were exposed to noise at 70, 80, or 90 dBA for 1 h daily during the first week after parturition. Litter size, birth weight, incidence of stillborn pups, and rate of neonatal weight gain were analyzed. Noise decreased reproductive efficiency by decreasing live birth rates and increasing the number of stillborn pups.

Figure 1.

Expansion of the vivarium. Illustration of the future annex abridging the existing vivarium and an adjacent research building (East–West section). The annex expansion is a 4-story building designed to be contiguous with the existing vivarium.

Figure 2.

Noise transmission from construction into the vivarium. Conceptual illustration predicting the radius of noise attenuation to vivarium rodent-holding rooms during construction activities occurring at breakthrough points on each floor.

Figure 3.

Experimental design. Duration and gestational timing of noise exposure. In the gestational study, noise was provided during the first, second, and third weeks of gestation (experimental groups 1B, 2, and 3). An additional treatment group received noise exposure from E2 (the peri-implantation period) through E7 (experimental group 1A). For the neonatal study, mice with litters were exposed to noise during the first week after parturition. (experimental group 4). Individual subgroups were exposed to either 70, 80, or 90 dBA.

Figure 4.

Ambient noise is increased due to human activity. The lines represent 24-h noise measurements taken from a rodent-holding room and are depicted as time-weighted, energy-equivalent noise levels (L_eq). Statistical distribution descriptors were used, L₁, L₁₀, and L₉₀, where the numerical subscript represents the measurement duration in minutes. L_max and L_min depict noise of the highest and the lowest intensities recorded during the measurement time period. Noise is increased during normal working hours, primarily because of human activity.

Figure 5.

Ambient noise in the vivarium. These representative 24-h spectral time-weighted averages (L_eq) of measured noise levels were taken from 4 rodent-holding rooms. The figure illustrates the noise generated as it correlated to frequency and human and mouse hearing ranges (shown above graph lines).

Figure 6.

Noise generated from construction activities. These noise measurements were taken during a jackhammer slab demolition on the first floor. High-decibel noise was present at high frequencies (greater than 8 kHz) well within the hearing range of mice.

Figure 7.

Noise affects litter size and the number of stillborn pups. Noise during the first (excluding the peri-implantation period), second, and third weeks of gestation increased the incidence of stillborn pups (Experimental groups 1B, 2, and 3). Noise exposure during the peri-implantation period decreased litter size (Experimental group 1A). *, P < 0.05.

Figure 8.

Growth rates of neonatal pups exposed to noise. Average growth weights of pups from similar-sized litters exposed to ambient noise (control, n = 80 pups; 70 dBA, n = 44 pups; 80 dBA, n = 60 pups; and 90 dBA, n = 52 pups). During the first 7 d after birth, the pups' weight increased over time as expected, and daily 1-h exposure to noise had no significant effect on growth rates.