Once outside the EU, the pesticide industry and its allies could persuade the Government to allow harmful substances banned in the rest of Europe to be used in the UK on the food we eat and in our public spaces like parks and playgrounds.
The vote to leave the EU will force the government to reassess the rules that govern the use of pesticides in agriculture, amenity and homes and gardens in the UK.
On the one hand, this could be a golden opportunity for the UK to take the lead in pesticide legislation by ensuring that the most rigorous, precautionary regulations are put in place to protect us from these toxic chemicals.
But on the other hand, the pressure to remove 'red tape' for the farm and food industry is strong. The powerful pro-pesticide lobby would like to see the current legislation watered down. If they succeed, this could result in:-
Greater exposure to pesticides that are linked to cancer, reproductive problems and endocrine disruption;
Higher levels of pesticide residues allowed in the food that we eat;
Increased use of pesticides that are highly toxic to bees and other pollinator species
What should happen?
PAN UK has already called on the UK Government to strengthen the current pesticide regime and make the UK a world leader in sustainable agriculture.  Today we have gone further by publishing a list of policy measures that the UK could adopt as part of a new plan to protect you and the environment.
Measures include introducing mandatory pesticide reduction targets, monitoring regimes, rewards for good practice and disincentives for bad, and more use of the precautionary principle.
But the risk now is that instead of adopting such a plan, the government will weaken pesticide legislation in the UK. So today, PAN UK is also launching a campaign to help UK citizens to place pressure on their MPs to let them know that the vote for Brexit was not a vote to dismantle environmental protection.
Politicians are being targeted by highly paid lobbyists from agribusiness who want weaker rules. We need to remind them that they represent us and they have an obligation to ensure the safety and wellbeing of the people and environment of the UK and that the priorities of any pesticide policy should be to protect human health and the environment.
How could weaker rules affect you and your environment?
Greater exposure to dangerous chemicals
At present, the UK is subject to the rules and legislation that apply throughout the EU. Whilst not perfect, it is one of the strictest regulatory frameworks for pesticides in the world. It was strengthened in 2009 when the EU moved from a 'risk-based' system to a more 'hazard-based' system.
This new approach means that any pesticide with dangerous characteristics - for example carcinogenic, reprotoxic or endocrine disrupting - should be taken out of use.
Currently over 100 pesticides are banned in the EU for health and environmental reasons, and more - including dozens of chemicals that are thought to be endocrine disrupting - are likely to be banned before we leave the EU. 
Successive UK governments have been very sympathetic to the pesticide lobby and actively opposed strengthening EU pesticide legislation.  Once outside the EU, the pesticide industry and its allies could get their way and persuade the Government to allow harmful substances banned in the rest of Europe to be used in the UK on the food we eat and in our public spaces like parks and playgrounds.
Last year the UK was among a minority of Member States that backed the re-licensing of the herbicide glyphosate - a probable human carcinogen.  Many other countries, including large agricultural countries like France and Italy, called for it to be banned.
In the face of this disagreement, the European Commission agreed to licence for just 18 months, meaning that glyphosate could be banned in the EU by the end of this year. Some EU countries are choosing not to wait and have already begun to restrict its use.
The UK government, responding to pressure from the NFU and chemical industry, continues to back glyphosate, and if the UK goes its own way on pesticides, it could remain in wide use here, needlessly exposing us and our children to a chemical that probably causes cancer.
More pesticides in your food, greater threats to bees and wildlife
Approximately 60% of the fruit and vegetables consumed in the UK contain residues of one or more pesticide.  The current system sets Maximum Residue Levels (MRLs) for pesticides and food, and for any pesticide that is banned from use in the EU, the level is set at zero.
This is not a perfect system, but it does help to reduce our exposure to pesticides. Yet some are pressing for less stringent MRLs once we leave the EU to allow an 'acceptable' level of residues for currently banned pesticides. 
In December 2013, the European Commission implemented a partial ban on three bee-toxic neonicotinoid insecticides  Once again the UK government opposed the ban.  This year, the Commission could decide to make the ban permanent in 2017 and even extend it to cover some other uses and more pesticides.
Highly vocal neonicotinoid supporters in the UK - including the NFU and influential politicians like former Environment Secretary Owen Paterson - want to see the ban overturned. They believe that once the UK is out of the EU it will be possible to overturn decisions that are based on a precautionary approach.
This would be a disaster for bees and other pollinators in the UK. We need a more precaution not less and we need to ensure that the farming lobby does not get its way on this issue.
What you can do?
These threats are very real and we need to alert politicians fast. We need them to grasp the greatest opportunity in generations to reduce pesticide use in the UK and switch to more environmentally friendly farming approaches.
Now is the time for the UK to set out a clear vision of a sustainable future for farming, food production and pesticide regulation so the UK can protect the health of its citizens, and become a world leader in, sustainable agriculture.
Brexit has been lauded as an example of democracy in action, but to be successful, democracy must a continuous process not a single question. Politicians need to engage with the people they represent, and we need to let them know what we want.
You can make a difference - don't stand on the sidelines while rules designed to protect the environment and our health are bartered away. The pesticide industry and agribusiness may be wealthy and powerful, but if enough of us stand together, we can prevent them from getting their way.
Keith Tyrell is Director of PAN UK.
Action: Simply go to our action page to send an email to your MP - we have created a sample message and it should only take a minute.