Regarding noise in forestry activities, it is clear that the duration of the activity can highly influence the effects of noise exposure. This can be seen as a possible area for improvement, if equipment is designed to perform faster, but might also cause concern under heavier working conditions confirmed by some of the measurements, which yielded noise levels at 106 dB(A) for chainsaws, indicating that the most effective margin for improvement would be obtained by best-practices that minimise the exposure.
The effects of excessive noise exposures have been analysed since the mid-1990s. A research article
[32] from 1996, based on a large sample of two thousand interviews with farmers, found that field crop farm operators were exposed noisy jobs, which made up as much as 30% of their work, while the lowest exposure levels (median noise 1%) was found among nursery farmers. In addition, smaller farms reported higher exposure levels compared to larger farms, given that operators of the latter were more likely to wear hearing protection devices. These results, however, are based on national data and self-reported information provided by farmers.
Tractor drivers, given the higher levels of noise generated in their activities, are expected to show a higher prevalence of hearing loss after 30 years of employment in agriculture. A study including drivers of medium and high-power tractors, performed in 2001
[33], assessed the chance of hearing impairment after 30 years of occupational exposure to noise from medium and high-power tractors to be between 13% and 37.9%. The risk of hearing impairment due to occupational exposure to noise that may cause an acoustic trauma was 37.9% for medium-power tractors and 13.0% for high-power tractors.
Hearing loss represents a health issue among farmers. Farmers also experience an increased risk of hearing asymmetry
[34], and the rate of injuries was higher for those exhibiting occasional use of hearing protection devices compared to workers that did not use them at all, suggesting that an irregular use of hearing protections could negatively affect safety. It must be also noted that such effects might trigger stress and fatigue in workers, affecting their sensibility to detect any early onset issues related to hearing loss. Further evidence of the impact of NIHL in occupational health
[35] shows that workers exposed to noise had a 52% increased risk of injury compared to unexposed workers, while these risks were far higher for workers with mild and moderate hearing loss, where chances increased by 7.87-fold and 4.48-fold, respectively. Such results indicate that a reduction in occupational noise exposure might improve safety in the workplace. Given the seasonal cadence of many agricultural activities, it has been found that summer and autumn posed higher noise risks among farmers
[36].
Farmers do not represent the only group exposed to NIHL in agriculture: family members and children are, in fact, often unrecognized exposed groups which should be included in prevention and protection programmes. Hearing loss in farmers may begin during childhood, where it can result from both noise, as well as ototoxic exposure that might be due to specific solvents and pesticides
[37], and this hearing loss increases with age. A high prevalence of NIHL, as indicated by Ref.
[38], is not the result of presbycusis, and this highlights the need to begin to prevent hearing loss among farmers at a young age. Another study
[39] showed that for 25 adolescents from rural areas, 44% of the mean daily noise exposures were higher than the NIOSH recommended exposure levels (REL) of 85 dB(A), while 18% of the 71 daily noise exposure measurements exceeded 90 dB(A). Another study from Humann et al.
[40], conducted separately for men and women in a large sample of more than 1500 participants, reported that short-term exposures from hunting and pneumatic tools should also be considered and assessed along with long-term common activities, given that exposure to noise from such activities was common between both farmers and rural residents; at the same time, the study showed the need for more precise analysis of NIHL in women, since performing the same activity might differ in duration. Specific research has also been performed on particular agricultural activities. For cotton gins, it has been estimated that 7 to 8 weeks of acute noise exposure with 10 months of respite from exposure can lead to NIHL during a working lifetime
[41]. Another recent study
[42] focused on the effects of both noise and pesticide exposure, finding that insecticides and noise exposure could separately affect hearing thresholds for high frequency sound bands or may have an additive effect, causing an increase in the risk of NIHL.
2.3. Noise Risk Prevention and Control
Analyses on noise exposures and effects provide a well-defined background for better risk prevention and control. Given the context, hazard elimination is not a viable solution: actions can aim to optimize vehicle engines and openings in cabs
[43] or reduce noise emissions in cabins
[44][45]. Regarding self-propelled harvesters
[46] it should also be noted that noise issue related to pressurised air or vacuum systems also need to be tacked at design stage. In some cases, like in tasks involving chainsaws, short breaks and better equipment that provide enough protection to the harvesting operators are required
[47]. Better designs can also lead to an easier identification of noise sources and thus reduce workers’ exposure, especially by models that allow the definition of noise source indices
[48] or by studying suppression effects for workers exposed to noise
[49] since transient Evoked Otoacoustic Emissions (EOAE) and Distortion Product Otoacoustic Emissions (DPOAE) examinations can be used as early identification of hearing damage.
Specific measures for mitigating noise risks also rely on HPDs and health programs or screenings. These aspects will be analysed in the following subsections.
2.3.1. HPD, Sensors and Other Detection Devices
Workers’ behaviours are an important aspect in agricultural noise management, since proper education and training that aim to list the benefits provided by HPD can increase workers’ willingness in wearing them: this approach can lead to better results, compared to mandatory requirements requested by laws or employers
[50] and can also be promoted in schools or by adding training on farm noise for rural youth to other training courses that involve noise protections such as firearm training sessions. Randomized trials about the use of HPD and their effects
[51] have also been proposed through the definition of test protocols, and the feasibility of hearing health education embedded in other already-existing and all-inclusive safety education programs has also been demonstrated to work out well as a booster intervention since it increased the chances of behaviour changes in wearing HPDs
[52].
From medical point of view, sensors can be deployed to analyse in real time the difference in cardiovascular performances while workers are exposed to tractor noise at various engine speeds
[53] or, for instance, evaluate how the operating conditions of different agricultural activities affect the main psychoacoustic parameters, namely loudness, sharpness, roughness, and fluctuation strength
[54].
2.3.2. Screening and Health Programs
Another well-known approach is based on exposure levels, but healthcare institutions play a key role in that sector since rural areas often have limited access to hearing healthcare facilities. In addition, some categories have different perceptions related to noise effects and hearing loss since they might tend to consider it as a consequence of their job that cannot be avoided. Low-cost hearing screening
[55] that could rely on community-based organizations, surveys regarding farmers’ beliefs on hearing loss mixed with noise assessments and educational sessions
[56] and methods to predict hearing loss by assessing the expected number of hours of hazardous noise exposure
[57] can be a valuable resource especially if they lead to a better description of the effect of particular activities especially in older people and in workers with a family history of hearing loss
[58].