Someone posted the link to The Conversation but here is more info.
Crumb rubber infill
"Crumb rubber from tires may contain for example various metals such as cadmium, chromium, zinc, aluminium and lead; oils containing various chemicals including volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs) such as benzo (a and e) pyrenes, benzo (a) anthracene as well as phthalates. Several of these are known or suspect carcinogens, neurotoxins and potential endocrine disruptors."
<a class="break-all" href="http://go.mumsnet.com/?xs=1&id=470X1554755&url=www.ncbi.nlm.nih.gov/pmc/articles/PMC5615587/" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5615587/
"We showed the tiny particles from the turf can become suspended in air above the field and inhaled by children playing on the field. What has become apparent is that microscopic carbon black particles break off from the crumb rubber and are small enough to be inhalable.
Additionally, the blades of grass can also break down into microscopic particles over years of exposure to sunlight and weather, forming a respirable dust."
<a class="break-all" href="http://go.mumsnet.com/?xs=1&id=470X1554755&url=theconversation.com/why-artificial-turf-may-truly-be-bad-for-kids-72044" target="_blank">http://theconversation.com/why-artificial-turf-may-truly-be-bad-for-kids-72044
Microplastics leach
Microplastics from artificial turf can end up in the ocean:
"- Particles are released to paved areas surrounding the field... and are subsequently released to the sewerage system via grates.
- Release of infill particles to the indoor environment, as the particles get stuck in sportsbags, shoes and clothing where they can be released to sewerage system via discharges from washing machines.
- Release to drainage via drainage water... to the sewerage system or end up in nearby streams due to heavy rainfall."
Carbon footprint
"Synthetic turf is a petro-chemical product which requires the use of virgin materials, high levels of processing and production, transportation and disposal at end of life. When considering the entire life cycle, these material impacts of synthetic turf significantly increase the total emission of this product and far outweigh the emissions that occur from maintaining natural grass."
Carbon sink
"Natural grass helps remove carbon dioxide from the atmosphere through photosynthesis and stores it as organic carbon in soil, making them important “carbon sinks.” A typical lawn (2,500 sq. ft./232 m2) converts enough carbon dioxide from the atmosphere to provide adequate oxygen for a family of four."
"Often artificial turf replaces a natural grass surface, so another contribution synthetic turf makes to global warming is the removal of a natural grass surface that reduces carbon dioxide, by converting it into oxygen"
End of life disposal
"Synthetic turf is not designed to break down quickly (that is one of its advantages) which means that when the surface has passed its useful life it has the potential to stay in landfill for long periods of time."
Soil regeneration and dust stabilisation
"...before installing synthetic turf it is recommended that all soil be heavily compacted. This damages soil structure, soil microbes and soil life. It can also significantly damage any tree roots in the vicinity."
Heat dissipation
"The replacement of natural grass with synthetic turf... can contribute to rising temperatures in urban settings, known as the urban heat island effect. Urban heat islands are created when natural grass and trees are replaced by impervious surfaces which absorb heat."
<a class="break-all" href="http://go.mumsnet.com/?xs=1&id=470X1554755&url=www.kimointernational.org/feature/microplastic-pollution-from-artificial-grass-a-field-guide/" target="_blank">http://www.kimointernational.org/feature/microplastic-pollution-from-artificial-grass-a-field-guide/
https://www.dsr.wa.gov.au/support-and-advice/facility-management/developing-facilities/natural-grass-vs-synthetic-turf-study-report/broader-environmental-considerations