In poultry, embryonic mortality from pathogenic microbial infection is preventable through simple, cheap and efficient preventive guidelines. In most countries, the sanitization of hatching eggs is the primary countermeasure to the attacks of pathogenic microorganisms on the embryo. Studies have shown that sanitizing hatching eggs with synthetic products such as hydrogen peroxide [1] and natural products such as clove essential oil [2] reduced the pathogenic microbiota in eggshells and increased the percentage of hatched chicks. These active materials are non-toxic, non-corrosive and non-damaging to the eggshell. However, unsatisfactory effects such as possible severe toxicity in embryos that led to their death were reported in eggs sanitized with formaldehyde [3]. Microfragments were found in the cuticle and the vertical crystalline layer in eggs sanitized with peracetic acid [4], and reduced hatchability was found in eggs sanitized with propolis [5].

The beneficial and non-beneficial effects of sanitizers in hatching eggs result from synchrony (favorable) or non-synchrony (unfavorable) factors, such as concentration and application time [4,6]. As mentioned earlier, it is clear that sanitizers, when applied to hatching eggs under certain conditions, can generate a repertoire of adverse effects that affect embryonic development. Embryonic health is undoubtedly an important aspect that influences the entire poultry sector. It is through a healthy embryo that a healthy chick will be born. In turn, if handled properly, this chick will become a healthy broiler that will reach the consumer’s table without undue influence on human health. At the same time, the poultry chain experiences significant economic gains for maintenance and growth. However, no sanitizers should be definitively rejected before being fully and continuously evaluated unless the compound is known to be lethally toxic to the point that humans cannot manipulate it with personal protective equipment. Human health must be a priority over all matters considered when choosing a sanitizer for hatching eggs.

Formaldehyde is the primary sanitizer in the routine sanitization of hatching eggs on European poultry farms (for example, Germany and Poland), as well as in Brazil and Egypt, among other countries [2,7,8,9,10]. However, it has genotoxic and cytotoxic properties [11] that subject poultry farmers and chicken embryos to a high risk of hazardous chemical exposure and possible irreversible bodily harm. Indoors, a short exposure not exceeding 0.1 mg/m³ (0.08 ppm) of formaldehyde is recommended to avoid damage to human health [12]. Cadirci [13] reported that the concentration required to reduce practically 100% of the microbial load of hatching eggshells is at least 600 mg/m³ (489 ppm) of formaldehyde, which is an excessively high concentration when compared to those recommended for human exposure. Therefore, formaldehyde needs to be removed from the routine sanitizing of hatching eggs.

2. Sanitizers and the Sanitization of Hatching Eggs

2.1. Objective, Optimal Timing and Methods for Sanitizing Hatching Eggs

2.2. Formaldehyde