Environmental campaigners are warning potentially dangerous chemicals are present in children's blood.
Researchers tested blood to see if chemicals were present
A study of seven UK families by the World Wildlife Fund and the Co-operative Bank found children were worse affected than their grandparents.
The WWF says the chemicals, such as Organochlorine pesticides, should be phased out to protect children.
But some scientists say the fact a chemical is present does not necessarily mean it is dangerous.
Researchers carried out blood tests on 33 people aged from nine to 88, to see if any of 104 man-made chemicals were present.
Of the chemicals analysed, 80 were detected. Children were found to have 75 chemicals in their blood, 75 were found in parents and 56 in grandmothers.
Eighty-two percent of the people tested had at least one perfluorinated chemical in their blood.
DEHP - which is present in many plastics - was found in over three-quarters of the volunteers, including children.
It has been suggested the chemical could disrupt hormone levels.
Chemicals, such as PCBs and DDE - a breakdown product of the banned insecticide DDT - were found in everyone, despite being banned in the UK at least a decade before the children were born, but on average the older generations had higher concentrations.
Some of the children were also found to have higher concentrations of newer chemicals, such as brominated flame-retardants - used in everyday products such as furniture and TVs, and perfluorinated chemicals - used in the manufacture of non-stick pans, than older generations.
The researchers say their findings suggest all British children are likely to be contaminated with hazardous chemicals.
Justin Woolford, WWF Chemicals and Health Campaign Director, said: "These results are extremely worrying because of the unknown long-term health effects of the majority of industrial chemicals people are exposed to.
"The contamination of three generations of UK families, including children as young as nine, with hazardous man-made chemicals clearly illustrates that industry and government have failed to control these chemicals."
The WWF says proposed EU chemicals legislation, known as Reach, currently being considered by member states for consideration, provides a "once in a generation opportunity" to bring in controls for these substances.
But a spokesman for the Medical Research Council's Institute for Environment and Health in Leicester told BBC News Online: "The world is composed of 'chemicals' and many of the most hazardous are natural."
He added that the presence of 'older' chemicals such as DDT in all age groups was not surprising as they were "ubiquitous throughout the globe and very persistent" - which was why they were banned.
He said: "At first sight it is rather worrying that 'new' chemicals such as the brominated flame retardants are occurring at higher levels in the children.
"But we would need to see the rest of the data to assess the actual difference in levels and whether this is statistically and biologically significant."