The way environmental factors affect fertility and cause effects over multiple generations may involve the epigenome of sperm. The mechanisms are far from being fully understood. These epigenetic marks can affect how the genes within sperm work without changing the underlying DNA sequence.
Yet, these changes can be passed down from a parent to their child. This can happen in two ways: when the germ cells that make sperm are exposed to contaminants of emerging concern, and when the sperm itself is affected. In both cases, epigenetic changes can be passed on to future generations who have not been directly exposed to the contaminants.
The following are ways that the environment is impacting male fertility.
1. Exposure to environmental toxins: Many environmental toxins, such as pollutants and chemicals, have been associated with a decline in male fertility. These toxins are often ubiquitous in modern society, and men may encounter them in their daily activities or through larger-scale environmental contamination.
2. Air pollution: Exposure to air pollution has been linked to increased sperm DNA fragmentation, chromosomal abnormalities, and impairments in sperm motility and morphology.
3. High ambient temperature: High temperatures, whether due to global warming or working in a hot environment, have been found to negatively affect sperm quality. Heat can impair sperm production and function, leading to fertility issues.
4. Chemicals in the environment: Environmental contaminants, such as pesticides, chemicals in plastics, and radiation, have been shown to have an impact on male fertility. These substances can disrupt hormonal balance and affect sperm production and quality.
5. Adverse working environments: Certain working environments, such as those with increased exposure to chemicals or radiation, can have a negative impact on male fertility. Occupational hazards can affect sperm quality and reproductive function.
Ref:
https://www.mdpi.com/1422-0067/23/6/3350 
