As PR chief at the Environment Agency, which exists to protect the air, land and water in England and Wales, she is a believer in practising what she preaches. One of her latest projects is to build a sophisticated composting system in her own back garden.
She starts reeling off her day-to-day energy-saving activities: 'Hang your washing out – don't use a tumble dryer, don't have baths...'
She volunteers: 'My greatest irritant is people who make political or personal decisions that ignore the environment or don't consider other people around them.'
McCallum has many years of heavyweight issues management under her belt, including two years as director of communications at the Department of Health.
She made her first significant mark in the comms arena handling the campaign that celebrated the 50th anniversary of the NHS. Yasmin Diamond, a friend and former colleague, now director of comms at the Department for the Environment, Food and Rural Affairs, says: 'Helen is hugely creative, energetic and passionate about public services. She worked tirelessly to build a coalition around the 50th anniversary campaign – no easy feat when you are trying to get politicians, health service managers, doctors, nurses, health unions and the royal colleges to work together.'
McCallum's skills at the Environment Agency, where she oversees 65 comms staff, will be called upon in full if the well-publicised bird flu virus hits British shores. While Defra will be the lead agency in handling any crisis, the Environment Agency will be tasked with ensuring all poultry carcasses are disposed of safely.
If they are buried, the agency must ensure no harmful agents seep into the ground or water supply, and if burnt, that nothing harmful is allowed to escape into the air.
'If this becomes an epidemic then we will play a significant role. It is not unreasonable to say "when" bird flu arrives – the question is rather, will it be huge?' McCallum asserts.
'Will it become a pandemic? So far there is no evidence. Will it jump species to become a human form of flu? This does not look likely.'
The Environment Agency's advice is not always considered sacrosanct – swathes of housing have been built on flood plains against its wishes, for instance.
'The agency is here to save us from ourselves,' says McCallum, adding that there is 'some room for improvement' in terms of making public bodies listen to its advice. Government is obliged
to consider issues that override the agency's concerns, such as its housing quotas. However, non-governmental bodies that regularly ignore its advice can expect to be named in the agency's annual report.
To escape from her serious daily undertakings, McCallum indulges in amateur dramatics in her spare time.
'I tend to play evil women who kill their children,' she declares, laughing heartily. 'As I get older I become more attracted to controlling, matriarchal characters.'
She is attracted to challenging roles packed with passion, such as Tamara in Shakespeare's Titus Andronicus. And although McCallum professes to have one more job in her, the attraction of retirement would be to devote more time to being a thespian in her home city of Cambridge.
McCallum describes the 13,000 staff at the Environment Agency as 'scientific', who typically 'hide their light under a bushel'. The same cannot be said of its effervescent chief communicator.