The recruitment of health workers and supply of medicines are key concerns for Wales after Brexit, a report says.
Public Health Wales (PHW) highlighted how the health of the poorest, those with lower educational qualifications, and those working in agriculture and manufacturing could also be exposed.
It called for those needing health and social care to be key considerations in a Brexit agreement.
The UK is due to leave the EU on 29 March.
PHW has compiled a wide-ranging impact assessment of the potential consequences of any form of Brexit.
Assessing the impact of any policy on health in Wales is a core part of PHW’s responsibilities and will soon become a legal duty.
In analysing the potential risks for Wales, the report looks at how access to medicines and health and social care staff from European countries could be affected.
Just over 2% of all NHS staff in Wales are from the EU and the warning echoes one made by the Welsh NHS Confederation last year.
But there is still uncertainty over what will happen after that date as Prime Minister Theresa May tries to gain consensus over a withdrawal agreement.
Analysis by Owain Clarke, BBC Wales health correspondent
Many experts so far fear that a “no deal” Brexit would be the most damaging outcome – although others naturally have a different view.
Uncertainties over exactly what will happen make it really difficult to accurately predict any potential impact.
But PHW said it has a responsibility to think about all eventualities.
Unsurprisingly then this latest analysis is very broad and could turn out to be imprecise.
Just take the assessment on smoking and alcohol consumption – for example.
Brexit might lead to reduction in smoking and drinking – if goods become more expensive and people are have less money to spend.
Yet if individuals are uncertain and stressed about the future then the opposite might happen.
The analysis doesn’t deny Brexit could have some damaging and significant short-term effects – for example on the staffing and the supply of new drugs.
But it also points out there could be benefits.
For example the UK and Wales could make bespoke and stronger policies in public health and agriculture as a result of having to leave the EU.
But that, it’s clear, will take time.
So for now focus, according PHW, is to plan to mitigate any risks.
But beyond that there needs to be a lot of research to address the “significant evidence gaps” about what exactly might happen.
The report says Brexit does give an opportunity to make positive change but “requires that the health of vulnerable individuals and communities is a central consideration in how Brexit is resolved”.
- Reduced or delayed access to new medicines, clinical trials and devices
- Impacts on the recruitment and retention of workers in the health and social care sector
- Loss or reduced access to future EU funding for research and development
Prof Mark Bellis, PHW director of policy and research, called for the health of the poorest people in Wales to be “paramount” in any Brexit agreement.
“Especially the health of those who are vulnerable to ill health through their reliance of health care, low levels of income or employment in sectors at risk through the Brexit process,” he said.
“Changes in the prosperity of Wales will fall hardest on such individuals and communities.”
He added the report was not a “road map through Brexit” but “a check list for those navigating the process to ensure that the health and well-being of the people of Wales is considered at every juncture”.