A senior toxicologist says a report about levels of man-made chemicals in people's blood is "alarmist".
The Jones family are among seven in Britain who took part in the survey
Thirty-three people from seven families including one from Powys, were tested for 104 substances.
Many of the chemicals are banned, claims the World Wildlife Fund (WWF) which commissioned the study.
But Professor John Henry, a clinical toxicologist from Imperial College London, said there was no evidence the toxins posed any harm.
The WWF said 60 leading independent UK and European scientists had signed a declaration calling for measures to reduce exposure to chemicals.
The latest survey is part of a campaign to ban hazardous man-made substances in everyday products.
It claims children have higher concentrations of certain newer chemicals than older generations.
Enid Jones, a member of the family from Llanfair Caereinion, near Welshpool, who took part in the tests said she was "shocked" by the results.
But Prof Henry said: "The tone of the report by the WWF is alarmist in my view. I wasn't surprised by it because these facts are already known.
"The amount of chemicals in the blood of the people tested would have been in parts per billion.
"There's no evidence that they are causing any harm to these people.
"I have traces of the chemical DDT in my blood like everybody else and I'm happy to pay that price because DDT has saved millions of people's lives."
He added: "The chemicals found by the WWF study would have been picked up from animals in the food chain.
"It just goes to show how slowly these chemicals break down.
"Perhaps we should be making more of an effort to create more biodegradable chemicals."
Elizabeth Salter-Green, head of WWF-UK toxics programme, said: "Over 60 leading independent UK and European scientists, including foetal and paediatric toxicity experts, have signed a declaration calling for measures to reduce exposure to both very persistent and very bioaccumulative chemicals, and hormone or endocrine disrupting chemicals.
"There is no doubt that chemicals are contributing to human diseases, including childhood conditions such as eczema, asthma and reproductive birth defects in baby boys.
"How many more eminent scientists need to speak out before the chemical industry takes full responsibility for the chemicals it manufactures?
"The only solution is better regulation - where hazardous man-made chemicals that build up in our bodies and interfere with our hormone systems are substituted with safer alternatives."
Blood tests were carried out across Britain
The Jones family is contaminated with organochlorine pesticides (OCPs) - a group of pesticide chemicals predominately used in agriculture.
Brominated flame-retardants - used on plastics and furniture - and Polychlorinated biphenyls (PCBs) formerly found in items such as TVs, were also found in the family's blood.
Mrs Jones said: "Despite our family following a relatively healthy lifestyle, I was shocked to discover that my children are being contaminated by certain man-made chemicals.
"It worries me that we don't know enough about what are in the products we use in our homes and their potential health effects. "
Alwyn, nine, the youngest member, was contaminated with a cocktail of 29 chemicals including OCPs and PCBs.
PCBs, despite being banned from new electrical equipment in the UK before he was born, have found their way into his blood.
He has eight more toxins than his mother Enid, who grew up surrounded by the chemicals. His father Arwel has the highest levels with 32 in his body.
"Surely as consumers we have a right to know and let our children grow up in a healthy environment?" added Mrs Jones.
"It surprises me that Alwyn has higher levels of chemicals in his blood than his sister as they have been brought up in the same way."
In 2003, 155 people throughout the UK were tested by the WWF for 78 chemicals found in everyday products such as televisions and furniture.
The toxins had been banned in the UK for decades, but every person tested positive for at least some of them.
Five members of the Jones family participated in the latest survey - grandparent Morfydd Thomas, 88; mother Enid, 51, husband Arwel, 43, and their children Alwyn, nine and Bethan, 11.