From Longman Dictionary of Contemporary Englishharmfulharm‧ful /ˈhɑːmfəl $ ˈhɑːrm-/ ●●○ adjective HARM/BE BAD FORcausing harm the harmful effects of smokingharmful to chemicals that are harmful to the environmentTHESAURUSharmful causing physical harm – used especially about things that cause harm to your health, the environment etcSmoking is harmful to your health.drugs with harmful side effectsbe bad for somebody/something to have a harmful effect on someone or something. This phrase is very commonly used in everyday English when saying that something is harmfulEveryone knows that too much alcohol is bad for you. damaging used about things that cause permanent physical harm, or that have a bad effect in other ways, for example on people’s opinion of someoneAcid rain has a damaging effect on trees and the soil.The allegations were very damaging to his career.Constant criticism is damaging to a child’s self-esteem.detrimental formal causing harm or having a bad effect on somethingEmployers are worried that the new laws will have a detrimental effect on their business. chemicals that are detrimental to the environmentpolicies that have been detrimental to the interests of old peoplenegative a negative effect is one that is bad and causes problemsThe car tax had a negative effect on car sales. the negative impact of the recession in the UShazardous hazardous substances are likely to be dangerous to people’s health and safetyHazardous waste needs to be disposed of safely.hazardous chemicalstoxic toxic substances, smoke etc are poisonoustoxic wastetoxic fumesToxic chemicals spilled into the river.pernicious /pəˈnɪʃəs $ pər-/ formal used about something that has a gradual bad effect which is not easy to notice, especially on people’s morals, or on their healththe pernicious effects of violent video games the pernicious effect of secondhand smoke
Examples from the Corpusharmful• The creation of the Premier League is therefore irrelevant and potentially harmful.• The problem is, what is good to eat and what is harmful?• Yet medicine is not a precise science and some treatments recommended, though they benefit most casualties, may occasionally be harmful.• Scientists tend to agree that most diets don't work and can be harmful.• Thorough cooking kills harmful bacteria, so be sure ground meat and poultry are cooked to the well-done stage.• Scientists have recommended that new technology be used to target harmful bacteria.• The destruction of the ozone layer will have a very harmful effect on the environment.• Doctors have warned against the harmful effects of smoking.• You should always use sunscreen to protect your skin from the harmful effects of the sun.• The new air pollution controls are designed to limit harmful emissions from industry and motor vehicles.• The cilia in the respiratory tract hasten the exit from the body of possibly harmful foreign material.• Is it a harmful geographic stereotype to suggest that southerners are a little bit poky?• Many of the products that we have around our homes are harmful if swallowed.• Residents living in the Jennyfields area of Harrogate were warned that the pills could prove harmful if taken by children.• The protests were aimed at ending the dumping of harmful industrial waste at sea.• Pushing kids so hard from such an early age is likely to have some harmful results.• If one is inherently harmful, so is the other.• As yet there is no proof that genetically modified foods are harmful to humans.• 80% of Americans think that television is harmful to society and especially to children.• The sun's rays can be very harmful to the skin.