How environmental problems grew with industry
Before big factories, people burned wood and made small waste. When machines, coal and oil arrived, factories made much more goods, and much more waste too.
- Air: smoke and gases cause smog and acid rain.
- Water: dirty water from factories reaches rivers and lakes.
- Land and waste: solid waste and chemicals pile up.
- Global problems: gases that thin the ozone layer or warm the planet.
After serious events, such as thick smog in cities or poisoned rivers, people started demanding rules, cleaner methods and better science. Problems moved from local (one town) to global (the whole planet), and so did the solutions.
Environmental risk and safety
A hazard is something that can cause harm (a toxic chemical, a hot pipe). Exposure is how much, how long and how close a person or nature is to it. Risk is the chance of harm: risk = hazard x exposure.
- To lower the hazard: use a safer material.
- To lower the exposure: fences, distance, ventilation, protective gear.
- Safety layers: design, guards, alarms, training and an emergency plan.
Safety also means checking: we measure the air and water, and keep records so problems are found early.
How industry responds
Factories now try to stop pollution at three points:
- At the start (cleaner production): use less material and energy, choose safer chemicals.
- In the middle (control): filters and scrubbers for smoke, treatment plants for dirty water.
- At the end (recycle and reuse): turn waste into new material, recover heat, safely dispose of what is left.
Companies also follow rules, publish reports and look at the whole life of a product, from raw material to waste. Cleaner factories save money on materials and are safer neighbours.
Try it: in the 3D, move the filter slider. Find the smallest strength that keeps pollution under the limit.
Key formulas and definitions
- Risk = hazard x exposure
- Pollution out = raw pollution x (1 - filter strength)
- Cleaning % = (raw - out) / raw x 100
Worked examples
1. A factory makes 100 units of smoke pollution per day. A filter removes 70%. How many units go out?
100 x (1 - 0.70) = 30 units.
2. The allowed limit is 30 units but the filter only removes 50% of 100 units. Is the factory within the limit?
Out = 100 x 0.5 = 50, which is above 30. No. It must raise the filter strength to at least 70%.
3. A chemical is very toxic (hazard 8) but is sealed in a tank so exposure is 0.1. Another is mildly harmful (hazard 2) but workers breathe it all day (exposure 3). Which has a bigger risk?
First: 8 x 0.1 = 0.8. Second: 2 x 3 = 6. The mild chemical has the bigger risk because exposure is high.
Common mistakes
- Thinking a very dangerous thing always means high risk. If exposure is zero, risk is small.
- Using hazard and risk as the same word. Hazard is the danger itself; risk includes how much you meet it.
- Believing one filter solves everything. Water, waste and energy need attention too.
- Thinking environmental care is only a cost. Saving material and energy also saves money.