org355: Firefighters | LSHTM Moodle

Happy New Year to all readers of Epi in the News.

The latest article comes from The Guardian.

Rates of prostate cancer, leukemia and oesophagal cancer appear to be 3.8, 3.2 and 2.4 times higher than the norm and overall firefighters have faced cancer death rates 1.6 times higher than the general population..

1. Are these prevalence ratios or incidence ratios? What goes into the numerator and denominator for the ratios?

2. What is the corresponding RR for "1.6 times higher"?

3. Explain why it is appropriate to standardize in the analysis. What characteristics would you want to standardize on, and which ones do you think it possible, logistically?

4. What are the mediating factors between being a firefighter and cancer/death?

5. What is the argument for this study's findings, from Scotland, being generalisable across the UK?

Those eating while wearing personal protective equipment were 1.8 times more likely to report a cancer diagnosis than those who do not.

6. This statement is counter-intuitive, unless you have completed an epidemiology module! Explain why PPE is associated with cancer. Should we ban firefighters from wearing PPE?

7. The article reports ratio measures. Explain why they should have also reported difference measures.

8. Does being a firefighter cause excess death?

Re: Firefighters

by | ISHITA GUPTA - Wednesday, 11 January 2023, 6:47 AM

Hi Sujit, Thank you for sharing the piece.
I am putting down my response below:

1. Are these prevalence ratios or incidence ratios? What goes into the numerator and denominator for the ratios?
Incidence ratios. Numerator includes risk/incidence respective cancer among fire fighters and denominator is risk/incidence respective cancer among gen population.

2. What is the corresponding RR for "1.6 times higher"?
RR=1.6

3. Explain why it is appropriate to standardize in the analysis. What characteristics would you want to standardize on, and which ones do you think it possible, logistically? (NOT SURE OF THIS RESPONSE)
Standardization is important as firefighters are being compared to general population and are not representative of the population from which they are selected.
Standardize on age, gender, work-hour shift time.

4. What are the mediating factors between being a firefighter and cancer/death?
Exposure frequency/time/duration, No. of years in service, smoking, Use of PPE, Hand/face wash post exposure, soot in nose/throat

5. What is the argument for this study's findings, from Scotland, being generalisable across the UK?
Fire brigade working practices are harmonised across the UK

6. This statement is counter-intuitive, unless you have completed an epidemiology module! Explain why PPE is associated with cancer. Should we ban firefighters from wearing PPE?
Use of PPE prevents cancer as it covers the body and face thus prevent inhalation, absorption via skin of harmful chemicals. However, if the PPE is not removed (soiled with chemicals) it can prove to be even more harmful, increasing risk of cancer due to increased (eating with hands that may touch soiled PPE) and prolonged exposure. This does not propose a ban in PPE as they are protective in nature and only practices around its use post-exposure need to be reconsidered.

7. The article reports ratio measures. Explain why they should have also reported difference measures.
Difference measures reports the absolute measure of association, in this case absolute number of excess cancer cases among fire fighters. It will be useful in assessing number needed to treat and plan interventions accordingly.

8. Does being a firefighter cause excess death?
Causation is governed by Bradford and Hill’s criteria
Strength- although ratios provided here are high, need to read the 95% Cis
Consistency: read results from studies done on firefighters in different settings
Temporality- its explained in this study as firefighters developed cancer after enrolment
Biological gradient-need to understand if more freq/duration has more risk. Partly explained by high risk among those wearing PPE while eating
And others..

Thank you.

Re: Firefighters

by | JUDITH MARGARET BURCHARDT - Friday, 13 January 2023, 10:51 PM

Thank you Ishita and Sujit,

Rates of prostate cancer, leukemia and oesophagal cancer appear to be 3.8, 3.2 and 2.4 times higher than the norm and overall firefighters have faced cancer death rates 1.6 times higher than the general population..

1. Are these prevalence ratios or incidence ratios? What goes into the numerator and denominator for the ratios?

Prevalence ratios - number of firefighters with cancer/total number of firefighters or if death is included then number of firefighters within a cohort who develop or die from cancer/ total number of firefighters in that cohort

2. What is the corresponding RR for "1.6 times higher"?

1+1.6 = 2.6

3. Explain why it is appropriate to standardize in the analysis. What characteristics would you want to standardize on,

Age and sex are logistically possible.
Ideally only working men would be in the control group, because of the healthy worker effect, but it is unlikely that statistics are available

4. What are the mediating factors between being a firefighter and cancer/death?

inhalation or ingestion of carcinogens from burning material eg benzene, soot

5. What is the argument for this study's findings, from Scotland, being generalisable across the UK?

That the exposure to firefighters in Scotland is the same as that over the UK because building and household materials are similar. Howevere, as Scotland is more sparsely populated than many other part of the UK it is possible that it takes firefighters longer to get to fires in Scotland, so they may be more advanced.

Those eating while wearing personal protective equipment were 1.8 times more likely to report a cancer diagnosis than those who do not.

6. This statement is counter-intuitive, unless you have completed an epidemiology module! Explain why PPE is associated with cancer. Should we ban firefighters from wearing PPE?

Firefighters who eat while wearing PPE are likely to still have soot in and around their bodies and will then ingest more of it than those who get changed and wash before eating. So PPE is acting as a confounder as it is associated with the mediator (burning chemicals) . PPE is not causing the cancer, and should certainly not be banned.

7. The article reports ratio measures. Explain why they should have also reported difference measures.

It is more important if the cancer is common than if it is rare. Difference measures give an indication of how common the cancer is. This is important for public health and for people considering how to best protect firefighters.

8. Does being a firefighter cause excess death?

We do not know. It is possible or even likely that firefighters have better cardiovascular fitness than others as this is required for their work. If they are less likely to develop cardiovascular disease then they will develop other illnesses as they get older. Prostate cancer for example is largely a disease of old age. Oesophageal cancer is known to be associated with eating burnt food and there may be a causal link with firefighting.

Best wishes

Judith